I visited a lot of churches and groups looking for a a place to explore and deepen my spirituality. Once I really made the commitment to show up and have a spiritual practice, I was able to find a real community of support at Zen Center. The people I've met have been kind, patient, and not too serious about themselves.
Every Saturday morning at 8:30am they offer free meditation instruction. Each week a different teacher leads the group and each time its different so you can go back more than once and get a different perspective. You can stay for the dharma talk which is followed by tea, visit the bookstore or check out some of the art. The building was designed by Julie Morgan (who also designed Hearst Castle) and has a small courtyard with a fountain and garden.
In my experience, Zen practice at San Francisco Zen Center requires a degree of patience and perseverance. People don't rush up and urging you to get more involved. They are more likely to meet you where your at, respond generously to a request, and quietly support your zazen (meditation) practice. For me the benefits didn't happen overnight but required sustained and regular effort. Over time I learned to value stillness and silence -- too qualities I never really understood before coming to Zen Center.
They have a library and great little bookstore where the staff are really knowledgeable. I have taken classes and retreats at all three of their centers -- Beginners Mind Temple in San Francisco, Green Gulch Farm Zen Center in Marin and Tassajara Zen Mountain Center in Carmel Valley -- and each has its on personality and attractions.