I've got some trail rides here in Pacifica if anyone is interested. Up on Sweeney Ridge and on Montara Mountain...
Andreas, who you can meet at the Arastradero Reserve practice sessions (i hope to make it there sometime soon) has some maps and whatnot of various off-road rides suitable for cross bikes on his great website here:
http://home.pacbell.net/hillmann/CyclingCalifornia/