After riding a $400 mountain bike into the ground, I bought a new full suspension 29er last May and have been driving the wheels off it. My go to place was Skeggs Point (El Corte De Madera) for longer rides. It is a former motocross park and probably the best MTB riding in the Bay Area. There are also hills and trails close to work that I hit at lunch or after I finish.
Needless to say, I also hunt off the MTB. Duck hunting running the levees, dove hunting covering some ground, deer and bear in the coastal range mountains ...
What I love about biking is that it covers more ground than running, you can really see a lot at a very nice pace where it doesn't get boring.
For Bay Area rides, check out this website. My goal is to ride every all off-road trail he has on there. I am about 10% done.
Bay Area Mountain Bike Rides
Let's go some time and kick some butt on the trails! PM me!
G