Been down Yampa and Lodore quite a few times. May, June and August trips.
Never had a bug problem on any of the camps at or above Jones Hole.
The camps below Jones tho even the one just below Jones have been thick with bugs the times we have been assigned there. Be sure you have tents with good mesh screens for sleeping and a couple of screen houses / tarps make cooking and eating bearable. Island Park has been a blood letting. If wind is blowing it is ok, but soon as the breeze hesitates or slows down the attack re starts big time.