Uh, fast bicyclists go 30 mph.
The road into Black Hawk from Denver is a long uphill, so bikes moving in that direction would be going slowly. Methinks the real motive here from Black Hawk is to cut down on the number of bikes on the highway, period. Personally, I think the cyclists are nuts, but they are engaged in a lawful activity according to the State of Colorado, so Black Hawk is akin to the City of Philly trying to pass its own laws in defiance of Pennsylvania gun laws.
Maybe in the Tour de France. On the roads here they go 10MPH with several in a knot that is very difficult to get around, and then when you finally get around them if you get a red light before you have a chance to get far enough away from them, they all run by you on the right, run the light and the red and form up to block you again.