I believe the only thing goin on in Ft Collins is the HobbyTown, on College just north of Harmony on the east side of the street, behind the Applebees or Chili's that's there. But - it's parking lot racing in the summertime only. I heard a while ago, that there was supposed to be a new offroad club/track in Cheyenne, but couldn't tell you any more about it.
In Colorado, for indoor electric offroad year-round, your options are:
MHOR in Aurora
High Desert R/C in Grand Junction
For Outdoor offroad in the summer, and primarly just gas:
Rat Raceway in Downtown Denver just north of LoDo/Coors Field
DirtWorks in Burlington, CO
Rocky Mountain R/C, the one on Boatworks Drive in Littleton has an outdoor track, it's off C470 & Quebec.
hope that helps!