There aren't too many rustic areas along the Front Range urban corridor any more. There's a commercial campground near the RR tracks south of Castle Rock. I think it's a Jellystone park or something awful like that now. There may be something out in the woods around Monument/Palmer Lake, but nothing stood out last time I rode through there. Maybe look at the Limbaugh Canyon or Red Rocks Road Trailheads for a stealth site.