'07 Fuji Roubaix RC, '04 Kona Hoss, '95 Cannondale RT2000 Tandem
Hey Biobob. The shop I used to rent from went out of business and the only other one I could come up with was The Bicycle Dr.http://www.bicycledr.com They claim to rent road bikes but I can't say I have any first-hand knowledge of their quality. I'll continue to ask around for you and post any other information I come across.
As for group rides, I'm sure you'd be welcome to join the Denver Bicycle Touring Clubhttp://www.dbtc.org Once again, I have no first-hand knowledge of the club but I've heard good things and keep meaning to check it out myself.
bike dr is nice small place and convenient to downtown and cherry creek bike path - it's at 9th and broadway.
also i believe the cherry creek bike rack rents for the day, they're in cherry creek and 2nd and detroit i think (2960 E. 2nd Avenue). cool little place, it's run by another bike shop to be a commuter hub, has repairs, bike storage, and other cool stuff. i've been in there once to fix a flat and they were very helpful - and it's close to everything too
enjoy your stay, weather's great - cherry creek bike path is fun, but downtown, capitol hill, congress park, and cherry creek (my neighborhoods), are very bike friendly. 7th avenue is nice wide east west street with beautiful homes, head past lower downtown to platte park too, great big REI store there in old warehouse