You can find examples of unmowed yards that are still beautiful and functional in many desirable urban-residential areas of cities. I'm thinking particularly of Hyde Park in Austin, Somerville in the Boston metro, Capitol Hill in Denver, Burlington VT, and much of Portland OR. It's not until you hit the suburbs where HOAs have dug in their claws and stand in the way of "cookie-cutter" ever becoming anything but.
In Colorado, check out the Colorado Native Plant Society or the Colorado Cactus & Succulent Society. Denver Botanic Gardens is also wonderful with outreach and education efforts, but they're not strictly focused on native plants (as far as I know).
To add to your list, the SeaTac area has a lot of amazingly gorgeous yards, and I'd say the majority of them are not your standard grassy yard.
Maybe it's because enough people have realized how nice their yard could be, maybe it's small spaces and hills, or maybe it's how difficult and irresponsible it would be to try to keep the grass green in the summer. Either way, I freaking love a lot of the landscaping around here, and have been extra-excited by yards massively overgrown with wildflowers, etc.
Beautiful No-Mow Yards: 50 Amazing Lawn Alternatives https://www.amazon.com/dp/1604692383/
Lawn Gone!: Low-Maintenance, Sustainable, Attractive Alternatives for Your Yard https://www.amazon.com/dp/1607743140/