Sure, I can do that sometime in May.  I have introduced quite few friends and co-workers to mountain biking.  I find that Arastradero in Palo Alto is one of the best place in Bay Area for beginners.  The course is roughly 5-6 miles.  It has a good combination of fireroads and singletrack, and it offers good climbing and downhills so that you can develop the skills that you will need for more technical rides later on.