There are a number of Zen groups in town offering informal practice opportunities.
The Floating Clouds, who are affiliated with San Francisco Zen center, meet on Tuesday nights for a 30 minutes sit and book discussion. The Clouds meet at various people's homes, so you would need to be on their email list in order to rendezvous with them. Contact Brian Goller at bgoller@gollerpublishing.com, for more information.
There is also a group, affiliated with the White Plum Asanga, who meets on Thursday nights at a private location, for sitting and dharma discussion. Contact Vincent Fortunato at vincentfortunato@mindtime.com, for more information.