Good riding at the following:
Wilder Ranch State Park – just north of Santa Cruz. As you take highway 101 into S/C, there’s a bike shop on the right called ‘Another Bike Shop’ and they’ll sell a map of the trails in the area (Krebs). Loads of trails and great riding.
Henry W Coe State Park – near Morgan Hill (home of Specialized). Seriously big area with some great trails. Ranger station at edge of western area is best spring point, then ride Corral Trail – Flat Frog Trail – Hobbs Road – Middle Ridge Trail – Poverty Flat Road. Seriously big loop and great fun.
Purisma Creek Redwoods OSP – park at the bottom and ride up Harkins Fire Trail then down Whittemore Gulch Trail (awesome singletrack the whole way down – big climb to get there).
Marin County, China Camp State Park (east side, just north of Sausalito) – park by the sea and do a complete loop – maps on t’internet – going anti-clockwise up to the radio mast then traverse right across the hill and back down to the sea. Fab trails and probably my favourite in the area.
Of the above, China Camp, Purisma Creek are nearest San Fran and Santa Cruz is next. Henry Coe is further away.