A little late, but
Denver Bicycling Touring Club has many levels.
Rocky Mountain Cycling Club - Intermediate to Advanced
Team Evergreen - Runs the annual Triple Bypass
There is a group that rides in Meridian every Saturday, I believe.
Check at Creekside Bikes in Parker - they have a weekly ride - pretty intense.
Parker has a cycling club
Highlands Ranch has a cycling Club
many, many others.