Thinking about moving to Colorado?

Primarily interested in the Boulder or Fort Collins area. Now I know there are other towns near these places, but I'm not sure how close they are, or anything about them. Places such as Loveland, Greeley, Longmont....etc... I see these names looking on craigslist and I'm not really sure what I'd be getting into. Anyone who can help me out, tell me a little bit about living and or working in either Boulder or Ft. Collins or their 'suburbs' would be awesome. Thanks! Also, I am in my 20s and single and I don't know anyone out there, I'm moving from the east coast.