Hate to break it to you but the Mormon belt extends well up into Idaho (probably all the way to Montana on the East side) and down into Arizona, and diffuses out quite far from there. Probably need to go through Montana or skirt the Mexican border areas to avoid it, but border areas these days come with their own issues self created by our government...
I lived in Idaho Falls (well within the majority Mormon area that extends farther North at least to Rexburg) and never had an issue, but I definitely knew I was not part of the club.
Utah Mormons are of a different mindset, they're on home turf in their promised land and they act like it.
There's a Mormon that runs a local business in my area. One day he puts his business up for sale because he wants to move to Utah to get closer to his faith. Ends up moving back and reopening a couple of years later -- turns out he was Mormon, but not Mormon enough. They don't like outsiders, not even the Mormons from out of state, which kind of makes sense with being a historically polygamous group which expels the young men who aren't in the "in" group. Breeds a mindset of exclusivity.