Is it too late for dry flies now, and if not is there a good fly for southwestern PA?

I've only fly fished one time before, but I've run into a lot of situations lately where I wished I had brought my fly rod.  Sooo, I'm dusting it off and hitting the Slippery Rock tomorrow for some much needed casting lessons. 

I've been a top water finatic since the first time I tossed a popper on Lake Arthur after dark, so I'm hoping to incorporate my two favorite things; trout and top water action.

Thanks in advance for any help!

Thanks Cold, I'll give em a whirl.  I am gonna head down to the local fly shop tonight and pick some up.  I have materials to tie, but I figured I oughta figure out for sure if i am gonna fly fish, before I start worrying about tying my own flies, haha. 

I'll see what they have for caddis hatch and go from there.  I got one trout the first time I went on a black fly, but I had a hard time keeping it on the top of the water.  False casting for me is attempting to cast while my fly is stuck in the tree behind me, haha.  Lots of work to do, but plenty of good water to learn on.

Thanks again for the input!