Oh nice! I went through Colorado Springs when I visited there a few years ago. Having seen the place, I really would love to head back with a MTB in tow!
Also, I'll have to check out South Dakota, because we went there too, and that place looks killer.
We saw about three groups of people that day on a 13 mile loop around the reservoir...so no, not too much. There are a lot of trails to choose from around here, so most of the time it's pretty good. Some get more traffic than others. This one scares off the timid because it is a loop with only one entrance. You have to finish, or turn around...