1. Do we need to rent a car?

2. Is 4 days enough time to visit?

3. Would it be feasible to make a trip to LA for one day?

4. I am going with my husband and we are both in our upper 20's. We are active and want to see it all! What are your favorite experiences???

Yes, you should rent a car if you want to see anything beyond the downtown area and Harbour.

I think 4 days is a perfect amount of time in San Diego but I wouldn't do a day trip to LA with that amount of time. There is enough to do in the San Diego area to keep you busy (La Jolla, Coronado Island, Balboa Park and the Zoo, Pacific Beach, Gaslamp, Harboor area, etc.)

I would figure out what you want to do before renting a car. If you stay in the downtown area, you can do quite a bit by using the trolley and bus system and cabs. Maybe rent a car for only a couple of the days for trips outside of the downtown area. If you are staying outside of downtown, then I would certainly rent a car. I would not do a trip to LA - there is plenty to do for 4 days in SD

Agree...but if you want to do it all, I would rent a car..we always do and the roads are good, singage excellent and you can see so much more in a limited mount of time..

A couple of shorter day trips, you could probably combine them into a single day....Wild Animnal Park neat Escondido and the Temecula wine regtion.
You can do a lot by trolly, cab and food but a car gives you a lot more options and you are more in control of the schedule.

I like SD better with a car. It is easier to get to the beaches, Cabrillo Monument, and several other places of interest. And it is easy to drive there.

SD is not really set up like bigger cities with great transit...it takes forever to get where you want..trolley is great.
Rent a car..check hotwire or expedia.
Since you are in your 20's, I would go to Pacific Beach/La Jolla or Del Mar/Solana Beach area.
Gaslamp/Downtown SD is very hip too.
Some really great deals with 4-5* hotels for super cheap.
SD is a gorgeous city and 4 days imo, is not enough..can you add another day or two?
If so, then go up to LA for the day.
When are you coming?
The beaches in the late summer rock..great beach swimming, Del Mar Race track is a lot of fun..tons of stuff to do and the weather is perfect.
We have great food too.

The question was "Would it be FEASIBLE to make a trip to LA for one day?"

Of course it is. It can be driven in 2 hrs. or less in light to moderate traffic.

Have not been to San Diego, but after doing some research on this city am thinking how long you want to visit (if you're going to "see it all") may depend on how much of Balboa Park you want to experience. There seem to be several days worth of attractions there, including the zoo, the main art museum, and many other museums of varying types.

I would not rent a car. We took the trolley.A whole day hop on/hop off. Great.Paul

No, it is no feasible to make a trip to LA in a day. It takes 2 hours to get around in LA once you get there. You will rarely find "light traffic".

We liked Wild Animal Park more than the zoo, but I would do both. The zoo owns the park and it is outside of the city about 45 minutes or so.

I think 4 days is about the right amount of time for SD. Have a fish taco, that's the food that I associate with SD.

I would definately rent a car.

Rent a car -- it means you can do in 3 days what would take 4 days if you use public transportation!

tovarich..
if you relied solely on the trolley to get you around SD, you would be sos out of luck seeing anything memorable.
it's great if you want to catch a Charger game and you are staying downtown..yeah, I would say go for it.
if you fly into the airport, they have a huge off site with shuttle service..things are pretty cheap here per diam for a car.

Native SD

ksucat--When tovarich writes, "We took the trolley.A whole day hop on/hop off" that makes it sound like the reference is to the City Tour bus which looks like a trolley but isn't. You are right about the real light rail trolley system--you can get from downtown to the Mexican border, to the Mission, Qualcomm Stadium (and Fashion Valley shopping along the way), Old Town, and not much else of interest to a tourist.

Here's my usual refrain--consider spending some time (perhaps centered around a lunch or dinner) in Hillcrest, which is about 1.3 miles north of the main way into the central area of Balboa Park from Sixth Avenue and is easy to get to from downtown by the Fifth Avenue bus.

...and you will not want to miss La Jolla, which is not available by trolley, is a LONG bus ride, and is a VERY expensive cab ride. Rent the car, for sure.

Coronado is fun, Old Town, Gaslamp, downtown. Great city to visit and 4 days is perfect.

We went on a whale watching boat cruise while there, it was very nice. Saw seals and whales and dolphins. It launched from downtown harbour, seemed a little sketchy at first but proved to be one of the most memorable things we did.

...sea lions...not seals....

Don't try driving up to LA. Traffic can be terrible. I drive from the LAX area to SD regularly and I cannot see why you would give up a minimum of fours hours of one of your four days for the drive. It's not particularly scenic, and it can be horribly slow. If you do decide to try it, look for the toll road that goes around the area where the 405 and 5 Freeways meet. I believe it's Highway 73. It will cost you about $5 each way, and if the traffic is bad, it will save you some time.

4 days is adequate as an intro to san diego but one can easily spend more time here. I'll join the chorus of folks saying get a car. There is so much you will miss if you don't have a car..... hiking Torrey Pines, kayaking La Jolla cove, see Coronado, La Jolla, Pacific Beach, Ocean Beach, Del Mar/ Solana Beach, Encinitas, Carlsbad, Balboa Park (which as someone who lives here, I haven't even fully done yet), downtown/gaslamp; there's already a week right there. Not to mention Temecula, Julian, wine tasting, etc.

I also would not go to LA on such a short trip; you will waste half your day in awful traffic.

Yes, rent a car. You'll spend half of your vacation waiting for public transport if you don't. Plus, as others have said there's so many places that maybe you could get to without a car (how do you feel about hitchhiking?)

When you're looking for a hotel take into consideration that hotels downtown probably charge for parking the car.

What do you want to go to/see in LA?