I'm going to be cosplaying Chrysalis, Luna, Tempest, and possibly Cadance (?).
I understand being shy; I'm a fairly reserved person in general.
As far as making friends at the con, I've found that most people at Bronycon are pretty friendly and willing to talk to people. There's a red/yellow/green card system in place, so you can look for people with green cards out near their badge to see which people are actively looking to converse (and having your own green card out is a good idea for that, as well).
If you cosplay, it's likely that people will approach you to ask for pictures. It's of course up to you whether to say yes, but sometimes that interaction leads to a conversation.