http://www.westernwheelers.org/ is a good recreational bike club in the Sunnyvale-Los Altos-Palo Alto area.
http://www.actc.org/ is a good club for Los Gatos-San Jose-Morgan Hill.
These clubs have fast rides and slow rides and welcome guests/beginners (on the slow rides, at least). They will show you the best local routes, as well as teach you riding and maintenance skills.