Not necessarily in PA mountains, but I have driven the West Virginia turnpike, Blue Ridge Parkway, and up and over other ranges in October. I like the cooler weather because the vehicle runs cooler up the grades. October can be a little unpredictable as far as night time temps, so you have to be prepared to run the air or the furnace. We packed for all weather, added a couple extra sleeping bags and blankets (we don't typically use the furnace) and had fun with it. Less crowded at the campgrounds too typically than in the summer. Sounds like fun!