*Disclaimer* This is not advice on how to make friends, that is something you should have learned in grade school. But...
Alta Alpina is a good idea for sure. You might just try going to somewhere like Keystone bright and early on a Sat. morning and ride slowly until someone passes you on the trail, then stick with them for the rest of the ride. They're bound to talk to you, whether they are irritated or not. Heck, they might even be looking for friends that way too. Last but not least, post in advance when you will be going riding on here. Chances are one of us jerkys will come join soon enough!
I'm not sure about you guys, but my regular group of riding buddies and I are riding buddies because we share similar schedules. Maybe you can ask a few co-workers?
