Denver is great, Light Rail, B cycle, Buses, Zip cars for easy renting. Lots of great ways to get around and lots of great shops, food and other needed stores within easy access of CU Denver/Metro or University of Denver.
Edit: Boulder is a 1 hour or 45 minute Bus ride ( depending on which bus you get) which has great opportunities for hiking, rock climbing, floating down boulder creek etc.
So i just applied to UC Denver for their new Applied Geography and Geospatial Science Program, the program is brand new and i am excited to be a first year student.