They are quite a few clubs in Norcal.
If you are looking mostly at having fun with no competition or timed laps, GFDA and Shelby club are pretty good,the only caveat being that even in the advanced group,passing is restricted to straights.
Or...as Matt sugested, you can try my club (NCRACING.ORG).
We are a "full service" club offering free SCCA licensed instructors,race school, opentrack from novice to advanced drivers with open passing anywhere on the track, time trials,relay race and full wheel-to-whell racing.
We use the best timing system (AMB)and conduct our races under "vintage"rules (meaning no contact)
We run mostly Thunderhill,Sears,Laguna,Buttonwillow,Reno-fernley.
We always have a few Vipers ( Gavin Gear from the Central CA VCA is a good friend of mine)and offer a free membership as well than a 30% discount to new member.
If you give me your adress,I will put you on our mailing list and send you a discount coupon.
Luc. 00GTS