I've never lived in Utah, but I grew up in western Colorado-which has a moderately large LDS population, and my brother lives in southern Idaho-which is pretty similar to Utah from a Mormon perspective. I have lived in suburban Denver (Lakewood-on the west side) since 1990.
Mormons are very nice people-they are honest, hardworking, and at least superficially friendly. They are somewhat exclusionary when going beyond that superficial level. Some families are fine with their kids hanging out with "gentiles" but dating, or going to prom might be frowned upon. Not all families are like this-like any religious sect, there are different levels. In general Mormons are far more observant that other religions in my experience-but I have never found them to be judgmental-or even have them seriously try to convert me. I have had a lot more of that kind of stuff with southern Baptists, frankly.
In terms of living in Denver. There are multiple school districts. On the west side of town, Jefferson County Public Schools is the largest district in the state-with 90,000 students. Schools are mixed-the wealthier areas tend to have better schools, the poorer areas worse schools. I don't think it's a spending issue so much as a population issue. Crackheads don't make their kids do homework-and some of the neighborhoods in the inner ring of suburbs have grown pretty marginal the last 30 years. Denver Public Schools, within the city of Denver proper, have a sketchy reputation. There are some positive schools-East, South, Thomas Jefferson, George Washington-that have produced some very strong graduates-but their average SAT scores are pretty dismal. I would avoid DPS. Cherry Creek Schools are reputed to be among the best in the city-they are southeast part of the metro area. The schools are generally large-athletic powerhouses. I've never met any exceptional graduates from those schools-I have met exceptional people from Denver South and East-schools without the strong reputation. Douglas County south of Denver (Highlands Ranch and points south) has been taken over by rightwingers. Their schools are in turmoil. The buildings are new-30 years ago there was 1 high school in the county-now I think there are six. Very fast growing area. Aurora is sketchy, areas up north I don't know much about, but there reputation is also marginal.
If you move to a wealthier zip code, your school will be better. Trail running is more varied on the west side-but areas southeast have access to Cherry Creek Park and the Highline Canal-which are wonderful.