Is there a local TV station you can contact? They might love a story like this complete with video, especially if the cops blow you off. "A special report tonight on STFU News. A motorist and a pack of skateboarders decide to turn a public road into a private movie set, nearly killing a cyclist in the process--and the local police don't seem to care...."
BTW...I doubt they would be issued a permit that would allow them to drive like that on a road open to the public.