They are everywhere, and shouldn't be hard to find in and around Pittsburgh.
For fly fishing (for carp), the only way to go is sight casting to carp that are already feeding. That is, unless you like to bow fish.;-)
I have never traveled anywhere to specifically target carp by any method. But I'm not above targeting them if I happen to see them while I am fishing for other things. Carp are not as cooperative on a fly rod as bass or trout.
Loads of them in the Allegheny, and the cool thing about that is that there is often a smallmouth bass or two just down stream of a feeding carp eating what the carp stirs up. Normally I would be after the smallmouth, but if the carp happens to take it, I am never upset by it.
I also have observed smallmouth just downstream of turtles, but this is a carp thread, not smallmouth.
When I say the Allegheny, I'm talking wide shallow areas where you can wade. I'm sure this applies to most streams as well.
As far as the funny looks go, I only give those when someone asks to keep a carp that I just caught, but I do that with steelhead as well.;-)