Karen, I have a similar situation , though at a much lower elevation. The orchids that do best for me are Ansellia Africana, Epidrendrum Radicans, Epi. Secundrum, Sobralia, and some of the Mexican Laelias, plus Zygopetalums. These live outside year round here, and will take temps down to the freezing ( for short periods) with no problem. These are not the big, floofy flowers though. As I see it, the hard water is the big issue. Ours is pretty bad too, so rain barrels are my solution. I have no way of pumping it, so do my watering with a 1 gal. pump sprayer. I keep a fan running in my tiny greenhouse, and if It is closed up, that helps keep the humidity up a bit, and the temps up also. I'm testing a Vanda in the greenhouse, but I think they need a lot more humidity than I can give them, and as with all orchids with exposed roots, they need daily watering. Phals have to be house plants here, where I do have a swamp cooler on my mobile home. It keeps the temps down and the humidity up. Some of the Cattleya hybrids survive in the greenhouse, but don't thrive for me, as a rule.
Hope this helps a little.
