I have been meaning to ride out at French Creek State Park since I moved back to PA. When I grew up in the Philly Burbs we would ride out there. Well actually we started riding at Valley Forge Park, which as far as we knew was not off limits back then. Back then there were not enough mountain bikers to worry the park rangers. Back to the story, once we got licenses we would go out to French Creek and ride.
My first good mountain bike was a Kona AA. And I have no idea how I rode these trails on a bike with that crap ass Marzochi XC-51 with 45mm of travel.
Actually all of the rock gardens are totally doable. Some of the down hills are kind of crazy because of the rocks. But nothing the turner could not handle. Which is also why I have no idea how I rode these trails… Oh I know why, the park is full of awesome, nice flowy, swoopy sections split up by rock sections that are challenging and rideable. I meant to ride for 2 hours but got lost and rode for 3 hours on Thanksgiving.
In the 14 years since I last rode there they have closed a ton of trails to mtn biking. But there are still so many trails open it is a great place to ride. 
It is a great place to ride and if you have the chance to ride in Eastern PA, definitely hit up French Creek. I rode it twice in two days.
But watch out for hunters. On Friday after thanksgiving it was a constant melody of gun shots. And the park is overwhelmingly open to hunting. Which is ridiculous.