That's so much better than PA's closed primaries! It's what I wish for TBH
Side note, I often wish I could live in CO for a while, but the altitude was really hard for the few days I visited Boulder once
If it influences your decision at all, your body does acclamate to the altitude. For a normal person with a normal activity level, you'll get most of the way there in the first month.
Altitude intolerance is almost always temporary — a couple weeks — and often ameliorates even during the early days with more water. It’s partly dehydration because the thin dry air & intense sun means we lose water faster just by breathing and sweating.
You do have to acclimate on intense exercise.