Santa Fe or Taos?+
Santa Fe is the bigger, easier one: galleries, restaurants, an airport shuttle from Albuquerque an hour away, and enough infrastructure that you never have to plan hard. Taos is two hours further north, smaller, rougher and far quieter, with a stronger pull for people who want to be left alone. If this is your first visit, Santa Fe. If you want silence, Taos.
Will the altitude affect me here too?+
Yes, more than people expect, because nobody thinks of a desert as high country. Santa Fe sits at around seven thousand feet and Taos higher, which is enough for a first night headache, restless sleep and quick dehydration. The dryness multiplies it. Drink constantly, go gently for two days, and remember that alcohol hits noticeably harder up here.
How cold does the desert get at night?+
Cold enough to catch people out in every season. Dry air at altitude holds no heat, so a day of eighty five Fahrenheit can drop to the forties overnight, and in winter below freezing is normal in the north. This is why every packing list here is about layers rather than one coat. If you are sitting outside after sunset, you will want more than you think.