spent 3 months in the states a few years back. The majority of people we met on the way had bought vans (in many state parks you pay for parking your car/van and the pay additional for tents so you save money if you can sleep in your van). The most popular choice seemed to be to fly into vancouver, and buy a car there as there are far fewer restrictions than in the states. Its a long long drive down to califonia, but you can stop at smith rock on the way down which is superb (two day drive from smith to san fran). I would also massively recommend goin to Indian Creek and red rocks if you can find the time.