On a per capita basis, Durango, CO. Great roads, tons of roadies, you can for for great flat rides in the valley, rolling rides to Vallecito or other locales, ride West up 160 for a nice moderate climb or go North to tackle mountain passes. The Tuesday night group rides are huge and offer everything from pro-class competition to the very moderate C groups, and there's awesome mounatin biking as well. Probably 330 days of sunshine, good access to the desert, and we have the Iron Horse Bicycle Classic. Plus we only have to drive 30 minutes to ski at the resort in the winter and have some of the best backcountry skiing to be found.
Downside would be the lack of much racing, but the Tuesday night rides are pretty racy.