It sounds like there's plenty of consensus for the Main Library at this point, but how big does the room have to be? 
 
I notice that the brand new Glen Park branch library has a meeting room that seats up to 50 people. It appears to be relatively undiscovered on Saturdays. It's a half block from BART and feeder MUNI lines, and there's lots of food options nearlby.
 
http://sfpl.org/librarylocations/mtgrms/mtingrms.htm
 
Teresa
sfmammamia