Reddit reviews Thomas Guide California Road Atlas: Including Portions of Nevada : Spiral

While winters in CA are pretty mild, they can be pretty wet for the SF Bay Area. I doubt you'll be where snow falls, so tire chains probably won't be a necessity unless you're planning on going towards Tahoe or into the High Sierras.

Most Americans only take a week or so of vacation time when they do get away from the grindstone, so 7-10 days is pretty much what we're used to.

A travel tip to help you orient yourself: Even numbered highways run East/west, Odd numbers are North/South, for example Interstate 5 goes through California, Oregon and Washington, while Interstate 80 crosses entire the country, pretty much coast-to-coast. (In Sacramento, there's the 80/80 split - Business Route 80 runs through Sacramento, I-80 cuts around it for a shorter trip).

If you want to save a few bucks, consider renting a car that's long enough for you to sleep in. Car Camping isn't an uncommon practice, and your car will probably be better insulated than a thin nylon-skinned tent.

Also consider buying a Thomas Brothers guide, as relying on your phone for maps/directions can be an issue in the more remote areas (and using a phone internationally can be very expensive).