Here is a lesson I've learned the long, hard way after 30 years of being a strong introvert: it's not how or where you meet people that counts. It's how you stay in touch. Look around you. Every day, in every situation imaginable, there are hundreds of ways to meet people. There really are. You could strike up a conversation with a stranger on a subway. You could ask for some advice from the girl ahead of you in line…
There are many car pools in the bay area that head to some of the local places (Byron, Lodi, and Davis). Most skydivers are also socially awkward and come from very different walks of life. It will give you the confidence that you can do something different and scary while also being novel enough that it's a conversation starter. Though, if you monopolize the conversation that's a negative.
It didn't fix all my social anxiety, but I can't say how much it helped.