It's been nearly 10 years since I've barreled down a single track.  My bike is long gone (stolen) and I suspect my tolerance for pain and physical abuse went along with it.  However, sometimes I find myself yearning for the sanctuary of a great ride.  Would anyone recommend a plan for maybe testing the waters to see if I may want to get involved again?  Is there a place you know where I can rent a bike for the day?  Is there a good ride in the San Diego area where I can get my feet wet again?