Hey,
Being a naive of Western Pennsylvania I can say the leaf show is spectacular. The height (peak) varies because of the weather (frost). Usually the last week of September to the first week and a half of October are peak. Attatched below is a useful PA link. When you view the site click around. Area 1 is the area of Ohiopyle: a short distance to Falling Waters....Good Luck on you plan for a fall visit to Western PA....Dianne

Here is a link that might be useful: Fall In PA

There's Phipps Conservatory, which also has outdoor gardens, though I haven't personally visited.

Here is a link that might be useful: Phipps Conservatory