I faced the same problem when I moved to SF last year. I'm not sure what the best way is. You could try going to meetups but its very hit and miss. Working from a co-working space (or even a coffee shop) might be helpful too. It all depends on how extroverted you are and how comfortable you are in approaching people and striking up a conversation.

I've been working on an iOS app to help hackers meet each other. Its called HackerLunch and I'm hoping to launch it next month (hackerlunch.com - sign up if you want me to email you when I launch).

The app basically pairs you up with another hacker everyday at lunch (or less frequently if you want). I tried to make the experience as frictionless and easy as possible. I'm hoping people will find it useful.