Winger:
Do we look like that trusting of a group of people? Really?
Would you believe me if I said `no'?
Mcgarnagle:
How long has it been since Karick's Bend opened it's kaer? Have our characters only lived in the outside world?
I picture it having been about 15 years since the doors first opened, and a couple years after that before people really felt safe moving upstairs -- which would suggest to me that Elven and Windling characters might consciously remember having been children underground, while T'skrang and Trolls are likely to have been born on the surface, and the rest were probably born in the Kaer but too young to consciously remember it. On the other hand, there's still a whole lot of it in the adults and the culture.
My initial thought is that the PCs would be a group of friends; a gang around the same age who hang out together and are probably, at least in their parents' minds, up to no good. Kind of skipping over the whole meeting-in-a-bar thing. (Not that I think Barsaive has an official drinking age, but, you know.) That's not something I'd be enforcing as a GM, though, it was just an idea, and is entirely up to you guys. You'd certainly know each other, though.