In addition to heeding Janisj's sage advice about pre booking hotels along the coast and within Yosemite, another thing to consider is that many coastal hotels will have two night minimums on a weekend and that bumps up to three nights if you are traveling on a holiday weekend.

Also, driving from Los Angeles through the desert to Arizona, there is more than the heat to deal with... there is the length of time and distance between road services. Make sure your fuel tank is full, that you are carrying plenty of water and that the car you are driving is in good repair. Those roads are very dark and desolate. Even traveling in the evening, the temperatures will be above 100 degrees and it can also be extremely windy.

Suggest you make sure your car rental agreement doesn't exclude Death Valley. We travelled in Sept 2012 and our agreement excluded DV.

Have a great time. Your itinerary covers some brilliant places and you see lots as you're driving too we've found. (We're always time poor on our trips too but we've created some amazing memories!!)

<i>I am not sure whether to add a day at L.A to visit some sights there</i>

Add some time to LA. It is a fun city.

Anyone is entitled to an opinion. Having one however doesn't make anyone right.

Someone can write, 'I THINK not pre-booking is a recipe for disaster'. That is simply an 'ad hominem' attack. Little better than name calling in terms of mounting an argument.

But if you can't get to at least a counter argument or the best, a refutation of a statement, then really you aren't much use as a debater.

Few here ever get anywhere near mounting a decent argument against anything. All you get is opinions with no evidence to back them up.

Here is what I have said. I have travelled a great deal without pre-booking. In many countries including all the places being mentioned in this thread. I have never been unable to find a room. Based on that experience and the facts easily found regarding hotel occupancy rates, I am quite comfortable saying it is no harder to wing it than it is to pre-book everything.

Now to disagree with that, someone has to willing to say that they have travelled many times and NOT been able to wing it in terms of finding a room. Not ONCE, many times.

That would be apples to apples, one cancels the other. Even better would be if many people said it. Even better again would be if someone provided a link to evidence showing that hotels are often fully booked.

But no one has provided any of that have they. Learn how to disagree properly, not just voice an opinion. http://www.paulgraham.com/disagree.html