S.F.
Hi!
You might want to come to the Bay View Community Center's playgroup - lots of 20-30ish moms come with kids ages 6 mo.-3 years old. I sometimes go on Friday and Saturday mornings (my son will turn 2 in a couple of weeks). People there are super-friendly and it's easy to just start up conversations. I have actually met people there that I see outside of playgroup as well!
Check out the Bay View CC website (just google it, I don't know its site address) for the schedule or give them a call.