Local Bay Area camping
I love to go camping close to home (Santa Cruz) when I have time. As suggested before, the Fairgrounds in Calistoga is excellent. A five minute walk in to town! Olema Campground is also a favorite in the North Bay.
Also love the Costanoa Resort. Right on Hwy 1 between Half Moon Bay and Santa Cruz. KOA runs this campground part of the resort. Not your typical KOA.
Last weekend I camped at Mt. Madonna County Park, on the summit of Hecker Pass, between Watsonville and Gilroy. Very peaceful and quiet with lots of hiking.
There is also a great San Mateo County campground right in Half Moon Bay, on the beach, not the one north of town.
Lastly, if you want to drive a little farther, I like Paso Robles. It's hot during the day but he AC keeps it cool inside.