I did the west coast drive in 09 and went to plenty of beautiful places.
SF is a beautiful city, at the right time of the year. It is probably my favourite US city because of the diversity within such a small location. Chinatown is quite unbelievable and the food there is beyond immense, decently priced too. Union Sq is a great hub and with plenty of places to sit and watch all the madness around you its great and surprising relaxing. Staying in the centre can be a bit pricey but booked far enough in advance the prices are reasonable.
The obvious GG Bridge and Alcatraz are must do's but i think Coit Tower doesn't get the talking it deserves the views from up high are magnificent on a sunny clear day, with views across the Bay and the Financial district. The trams are another thing to experience, the speed and angle they get! Plenty of other things to do including shopping (unfortunately) but Pier 39 is a nice place to eat and hang out too. Fish doesn't get much fresher than that.
A drive up the coast is a must, we stayed in Monterey and Santa Barbara and the like but the best point was the Big Sur. It is stunning.
Vegas is very very hit and miss, if you like tacky exaggerated Americanisation of everything then you will love it. If not then give it 3 days and move on quickly. Yosemite like someone said before is a beautiful beautiful place with so much to see and do and staying within a good hours drive of that area can be cheap and quiet after the hustle and bustle of Vegas and SF and even LA if you choose to go there.
Driving is tough work over there often with little to look at out of the window. But thats just me, i loved it in 2009 and in the summer its arguably one of the best places to be.