I'll throw in a vote for Wilmington, NC. I've only been here a few months after moving from Denver, but so far its enjoyable. Riding is possible throughout the city thanks to some great trails and bike lane infrastructure, and this being the South there are far fewer fitness fanatic than in Denver, so not much bike traffic to speak of.
Wilmington has a University of North Carolina campus and all the nightlife that goes with a couple thousand undergrads. Also, we are a bit of a destination town during the summer months and there are parties and festivals nearly every weekend. I'm not sure if that meets your requirements for a nightlife. Don't forget this is still a very "blue law" area where pretty much everything (including the LBS) shuts down on Sundays.