I just got back from a forty day camping trip to northern California where it was nice and cool. We belong to ThousandTrails, Naco so we stayed at SnowFlower preserve which is right next to Crystal Lake and high timber. It had water, electricity, but to dump you either had to go to the dump site or pay for the wagon to come to your coach and pump the tanks out. But the sites had plenty of room to accommodate big rigs.
After we left that preserve spending 21 days there, we decided to come back to southern California using hwy 395 which has lots of state and federal parks. My coach is 38' and I had lots of problems trying to find a state park that would accommodate anything much bigger then a 30' motorhome. Most of the state and federal parks were full or reserved way ahead of time. I ended up paying big bucks to stay in privately owned camp grounds. They were nice next to good fishing areas, but expensive.
Most of your state parks IF you can get reservations run around 17 to 29 dollars per night. Federal parks are about the same unless you own a Golden Age Passport, THEN you can stay for nine dollars per night. Mind you that none of the state or federal parks have full hook ups. You will be luck to just have water.
Like somebody else mentioned TTrails does offer a lot with preserves right next to beaches all the way to the Canadian border and it more then pays for itself if you enjoy camping.