Phoenix: Don't move there, the place really does suck. I was just there today.
Colorado Springs: Never been there.
Salt Lake: Do not move there, it sucks worse than Phoenix and that's hard to do.
Boise: Worse than Salt Lake in some respects, better in others. It's a wash on which one is worse. Both are cold in the winter, too.
Basically, for good weather and livability, Florida and Southern California are the only reasonable choices. Don't move here, though, because it really isn't a very family/pets/etc-oriented place.
If you were up for cold, there are many really great places that might work...