Colorado is pretty much ‘live and let live’. You’ll find a bit of everything, religious-wise, here. In my immediate neighborhood, I often joke that the main street of my neighborhood should be renamed “Church Avenue” because in a mile-long stretch, there’s a Catholic church, two Baptist churches, a Lutheran church (which given the proximity to my house would be dead useful were I Lutheran, because I could pretty much roll out my front door and be there), a Seventh-Day Adventist church, a Mennonite church, a Methodist church, and while I haven’t seen them, I know there’s a Jewish temple somewhere nearby (I’ve seen the men with the long, curly sideburns and prayer shawls walking through my neighborhood), a Muslim mosque (my next door neighbors go there), and a Buddhist temple. And a handful of other Christian denominations that have set up shop in the strip malls (that seems to be a ‘thing’ here in Colorado, I’ve never seen anything like that anywhere else I’ve ever lived.) And there’s a good-sized pagan presence here too.
Basically, whatever you’re looking for so far as religion goes, you’re going to find it fairly well-represented here. Really not going to be a problem. Colorado Springs is more heavily on the Evangelical side (Focus on the Family is headquartered there), Boulder’s probably a little more casual, Denver’s somewhere in-between the two. My experience, anyway.
Back to the main street of my neighborhood–some friends of mine had been looking at the service times on the marquees and had joked that if you were a Christian who was uncertain which denomination was the right one, you could just time it and start with the Catholic mass first thing, then go to the Baptist church right after, then the Lutheran church, and so and so forth, and just get 'em all in one day and have your bases covered (except for the Seventh-Day Adventist one, obviously.)
Something to keep in mind–I don’t know what your budget is, but Boulder is
expensive to live in. If it’s a case of a job being there, there’s some communities that would be close by, but not as expensive (Broomfield, Longmont, for example.)