This social is every 2nd and 4th Friday of the month. It's usually very well attended and there's a wide range of people from beginning students to native signers.
The flyer from NorCal Services for the Deaf & Hard of Hearing says to join others afterwards at the nearby Red Robin for dinner and/or drinks. Usually some attendees of the social head over there well before the 10:00 social end time. Some may go before the social too, but I'm not sure of how many or if they do that regularly.