I am from Kittanning, about 1 hour north of Pittsburgh.
I know of approximately 14 Grand Prix's, and most of them are kept in pretty good condition, which is difficult if the GP is used all year round due to the amount of salt dumped on roads.
I attend car shows at least once every weekend, weather permitting. There are some weekends that I show my GP all 3 days. There is one other GP owner who also goes to show every weekend.
Among the 14 GP owners, I would say 8 of them regularly post updates and talk about the w-body scene on Facebook.
So, in comparison with other areas who have 2-3 times as many GP's, I think the Pittsburgh area, and western PA in general, is still quite active.