We did a lot of riding in the area last weekend. Actually we were camped at Camp Williams on East Fork so we started out from there. I did Little GMR early in the morning before my wife woke up, then we rode up 39 to the 5000' sign. After descending 39, we hung a right onto the path towards Cogswell.
When we take our daughter up there, we'll park at the parking lot at the entrance to the path. There were actually lots of people parked there. The path was filled with walkers, joggers, hikers, fishers, and parents with kids on toddler bikes. The river was flowing, and the trees kept the path nice and shady.