I am actually from Beaver County so umm... What kinda riding do you do? I race hare scrambles and there is a place called Marienville. Its in the Allegahny National Forest.
I'm about 35 miles north, in Butler. Not as much riding around here as there used to be, but my son and I are able to ride on a friend's farm about 1/4 mile from our house. We also ride at Marienville (great trails), and Wellsville, OH.