I'm not in the Bay Area, but I am part of a group in Portland that meets for an hour in the morning once a week so I thought I'd share my experience in case you want to try to form your own group.
There are probably 15 people in the group total, and we usually have 6 to 10 people show up in any given week. Everyone knows everyone so we don't have to spend time on introductions. We divide up the time by how many people (10 people = 6 minutes each). Everyone says: 1) what is your biggest challenge right now? 2) what do you commit to have completed by next week. 3) one or two asks for the group. We tried combining 1 and 3, but sometime people would assume that their biggest challenge could not be solved by the group. But often someone can help, even with the big things. 6 minutes goes by quickly because there are always 2 or 3 people with ideas on #1 and #3. I almost always get something from this group and quite like the format.
If you are looking for a venue, and there are co-location office spaces near you, I bet they would let you hold the meeting there. You are bringing them potential/future customers. Good Luck!