This thread's gone cold, so at the risk of telling you what you might already know by now I'll give you a few leads.

Google the following terms:

"spectrum ride" -- it's a ride that starts in Sunnyvale, goes up the Peninsula, and has riders with abilities ranging from beginner to pro. I've never been on one of these rides, but from what I hear I have a feeling they would suit your desire to advance quickly.

"velo girls" -- a respected group of female riders of all ages. I hear they're very encouraging. I highly recommend checking them out to see if they're a fit for you.

"alto velo" -- some fast riders. When you're looking for a hard core ass-whipping, go here. Or so they say.

Good luck!