I live out here in the napa valley and Berryessa is cool there's resorts up there that rent campsites, most of the time during big weekends there's young folks up there gettin rowdy so you can stay up as late as you want cuz there's usually a lot of cats doin the same.
Dillon beach in sonoma county is a cool spot there's sand dunes through out the camp sites which make for a good spot to take over and throw up tents in but there's lots of old people with RV's this time of year.
I've heard a lot of good shit about the american river or whatever its called up past Sac I might have to take a camping trip out there and hit up the rafts.