I haven't been riding in a while, but I used to do the China Camp ride up in San Rafael, a short drive from San Francisco. It's a great ride but isn't too challenging.
Mtn Biking Trail Locations
A Map of Mtn Biking trails in NJ, feel free to add you favorite trails to the map!
*I am not responsible for wrongly placed trail locations, and please only place legal places to Mtn Bike.
-Thanks and Enjoy