I'd reccomend going to meetup.com and setting your location to SF. My profile of interests matches yours and I found around 300+ groups with regular meetups that were fun.

Note: there are also lots of conferences that are held here but those usually require not-insignificant entry fees (they're paid for by your employer normally) and there isn't a single resource that easily lists all conferences available in the area. I'd start with the meetups since they're usually free and take usually place after normal working hours.