I thought I'd give more knowledgeable folks a chance to reply, but having heard nothing, either they aren't so knowledgeable or they aren't here!
The CA Old-Time Fiddler's Association holds (or used to hold) a monthly jam in Palo Cedro. If you haven't already checked with the Oaksongs Music Society, they might be able to steer you somewhere. If none of that works you might try posting on the CBA message board.
Good luck! Picking is so much better when done in groups.