Marc, Herndon is in northern Virginia near DC.
MpinPoint, when you remove the construction sites from your list, I can't think of any areas off the top. I know that there are more than a few construction sites up there and would recommend using them. Any new housing developments? They are usually great for "off road" running.
I imagine that there are a few BMX or Motocross tracks up there. They usually welcome RCs for a little fun. Other than that, drive a little bit away from Herndon and look for some farm land to play on.