Hi! I am not going to CU but I did my undergrad there so can answer questions about the area. Graduate students typically live in Boulder, but I know a few that commute from Boulder. As a student you'll get a free regional bus pass that makes commuting from Denver super easy (also gets you to the airport for free!) I don't know that a ton of students live in Broomfiled, there is honestly not much there besides houses and families. My fiance grew up there and its just pretty boring town lmao. I think Westminister and Longmont are better options that are a little closer too if you're looking to be outside of Boulder.