Just spoke with the desk sergeant at the Rock Creek station. Cycling on Beach Drive is perfectly legal but they can ask you to leave the road if you are holding up traffic (not sure if DC traffic laws state this but this is Fed land). I explained it was early in the morning (to avoid traffic) and that I was doing about 20 mph on my road bike. He then asked for the officer’s name, etc. When I told him I didn’t get it he said he would pass my concern on to his team.