In preparation for doing the Cali Triple Crown this year, I signed up for the Davis Bike Club email distribution list so that I would find out when registrations opened for the Davis Double Century. Although the event has long since been done, I'm still subscribed to the list because it shows how a good club is run. There are constant updates about the NUMEROUS weekly rides, calls for volunteers for their big rides (which, if the Davis Double was any indication, are extremely well-organized and supported with military precision!), stuff for sale, and general tomfoolery.
When I was visiting on my California recce trip at the end of last year, I stopped in Davis and did one of the weekly rides with the club. We rode from Davis to Winters, to one of their regular coffee stops, and they suggested an additional easy loop I could do to make for a longer ride. Very pleasant.
So check out their web site, and get on their email list. I think you could do far worse for a club to be part of.
Luis