Yup, I actually organize rides where I get friends and friends of friends to tag along, and it ends up being a natural way to make new friends and so called "network".
Hiking works great too, and there are lots of great hiking routes along the purissima hills in the SF Peninsula.
I do similar things, but also as part of getting new people into mountain biking and building new, legal, open-to-bikes trails. It's pretty amazing the diversity of people that I've ended up friends and acquaintances with; people who I wouldn't hesitate to call up (or hesitate if they called me) looking for some professional help.
Hiking works great too, and there are lots of great hiking routes along the purissima hills in the SF Peninsula.