Yes, that would be the purpose: To include something interesting (Joshua Tree NP) on your way from Grand Canyon to L.A.
The main park entrances are on the Northern boundary of Joshua Tree, one in the town of Twentynine Palms, the other in the town of Joshua Tree. While there are many motels, hotels and food options on the Northern boundary of the park (Yucca Valley has the most), there is next to nothing to do there in the evening aside from relaxing on or in your hotel pool, have dinner, and a quick trip into the national park in case you can get there around sunset. It is amazing to see how the desert comes alive.
While the visitor center is only open during normal business hours, the roads in the park are always open.

If you prefer some more choice of evening entertainment, you should overnight in Palm Springs proper. But this will mean some back-trekking (30-40 minutes) next morning to get back to the park entrances. Palm Springs has a very nice and lively downtown area with tons of restaurants.

Check out the maps to familiarize yourself with the logistics to get to and drive in Joshua Tree NP:
https://www.nps.gov/jotr/planyourvisit/maps.htm

Ok, wonderful, thanks!

Spirit Airlines charges for everything, including carry-on luggage. That's how they make their prices look so much lower. Also check Southwest - keep in mind that they leave from Midway (MDW) and not O'Hare in Chicago. Right now they are only taking reservations through August 10, but those fares are running $178. They allow you 2 free checked bags and carryon. Southwest fares will not be seen on aggregator websites, you need to go to Southwest.com.

Great! I didn't know that company, I will be checking their web on a regular basis to see when the reservations for September are available.

Regarding Spirit, as you say it seems that they charge for everything, but UA and AA also do it, and for late august and early September from Monday to Friday Spirit charges "only" 168$ with seats and luggage (UA and AA as well but with no checked bags nor seats). I hope that for late September fares remains the same in Southwest or Spirit ...

I would stop at Henry Cowell Redwoods on your way to San Francisco instead of Muir Woods which requires reservations. I haven't been to Muir Woods since the reservation system (maybe it's less crowded now?) but find Henry Cowell more enjoyable. After that, you can decide if you want to head inland toward Silicon Valley or take the coastal route along Hwy 1. Hwy 1 north of Santa Cruz isn't as dramatic as Hwy 1 south of Monterey but is still quite scenic. There are also a few places to see redwoods in Big Sur. The easiest to access are at Pfeiffer Big Sur State Park.

Definitely check Southwest airline. 10000% better than Spirit and they don't charge for checked bags or beverages on board.

"Janisj, you say that Las Vegas – Zion – BC is too much few time for Zion, but … LV – Zion NP takes 2,5 h, so we could be there at 10.00h – 11.00h am I guess. Sunset that day will be at 18.33h, so we would have at least 6-7 hours for Zion. It is not enough?"

There is more to see and do in Zion - you should plan on spending the entire day there and then drive to Bryce Canyon the next morning.

"Regarding Silicon Valley, I though that it was in the middle of our way to SF, coming from Monterey, but according to your comments I guess it means to take a quite longer route, isn’t it?"

Silicon Valley is between Monterey and San Francisco. - but it is not a scenic area to tour around - you will want to get through there as directly as possible. When you are 'in' Silicon valley you really won't see anything except strip malls and apartments and shopping centers and maybe a tech headquarters if you happen to be on the right street. It is a huge suburban population center with a LOT of traffic. But if you really want to see one of them -- Googleplex is just off the 101 highway.

If you visit Henry Cowell State park (better and easier than Muir Woods) you can take a route that will take you very near Google on your way to SF.

Henry Cowell NP seems really nice, and Pfeiffer Big Sur State Park as well, thanks! I still have to get more information about the big sur days but I'll try to try to fit at least one of this parks on the route.

Regarding Zion, we may use the extra-day we have between Las Vegas an Zion, so we could use it to rent the car in the morning with no rushes, going to Hoover Dam, and after that heading to Zion stoping maybe in Valley of Fire. Next morning we would be very close to Zion so we could start early in the morning. Does it make sense?. It would be as follow:

- Day 5: LV
- Day 6: LV (car rent) – Hoover Dam - Valley of Fire - Hurricane (is this a good place to spend the night near Zion?)
- Day 7: Zion NP - Bryce Canyon.

Not a recommendation to change itinerary again, but I just needed to say this once: In my personal opinion only, the most spectacular way to approach "John Wayne" country is from Denver.
When you land on a morning flight from Chicago, you can see the vast plains that you just crossed to the East, and the majestic Rocky Mountains in the West.
Once you get away from the Denver metro area, Interstate 70 starts to climb and takes you through the mountains. I would even say that this one of the most scenic motorways/freeways you can drive on, with nice little mountain towns to explore in no time, or to stop at for lunch, like Idaho Springs or Glenwood Springs. Overnight somewhere in/near Grand Junction, or further East, depending how much exploring you do in the mountains.

Next morning you drive just a few miles to the West, and the scenery changes dramatically (again) as I-70 goes down again into Utah - where you would stop at Arches NP, maybe also check out a bit of neighboring Canyonlands NP. And spend next night in Moab.
Moab > Goosenecks State Park (Horseshoe Bend is not the only place where you can see such a bend, and Gooseneck is a quick "drive in" to the edge) > Monument Valley > Page > Bryce Canyon > Zion (?) > Las Vegas

I know that it is heresy, but I put the question mark on Zion just because I find the shuttle system so time-consuming for someone who is on a somewhat time-constrained road trip
https://www.nps.gov/zion/planyourvis...tle-system.htm
It's really just my personal bias, but I find it kinda hard to enjoy natural beauty and scenery when I'm part of crowds and wait at bus stops to get squeezed into the next shuttle to make it to the next viewpoint.

In Las Vegas, I'd return the car and fly to Santa Barbara, skipping all of L.A., including the hassle of LAX, and picking up Highway 1 there.
As you probably guessed already, I'm also biased against L.A. - especially when I am forced to divide my time between L.A., San Francisco, and the drive (and stops) on Highway 1.

Anyway, that would be my plan, not your plan.
And since it is your vacation, you should do what you want.

NO, Hurricane is not a good place. Stay in Springdale instead.

PS I agree that the shuttle is annoying as hell. The park has become overwhelmed with traveling Europeans and Asians. Maybe this fall will be better if the latter numbers are decreased due to coronavirus.

Now we just see the eastern part that connects with Bryce and skip the main bit, but as it's your first time, you probably will be on the shuttle.

Denver route sounds really good, but I guess I will have to search for John Wayne in Monument Valley, because Denver would mean changing the planning again and I don't want to start again since I'm quite happy with the current plan and I need to start looking for hotels and reservations, but thank you for the idea, I will keep it for my next trip to the USA. I saw the video about Zion (very useful information!) shuttle system and yes, it has pros and cons, lots of cons but I guess it should be worse previously, with lots of cars (and pollution) inside the park, I don't know, it's only an opinion and I don't know how it was previously. What it's true is that nowadays there are people everywhere, including all of us ...

What I have realised watching the shuttle system video is that as you have said, we should dedicate the whole day to Zion.

I have just book a room in Hurricane, thanks!

Why Hurricane? It's awful!! Springdale is closer and better place for Zion. I don't see ANYONE who has recommended Hurricane, maybe I missed it. Or maybe you missed it.

No one missed anything, i got confused writting but I actually booked at Springdale

MUCH better!