Sometime this year we will move to Belen, New Mexico which is strictly Santa Fe country. Will I have to throw away all my M&StL stuff and buy all Santa Fe equipment?
No, just leave your M&StL models out on the patio this summer, turning them occasionally. After about a week, they'll be nicely bleached and sandblasted, all ready for new orange or mineral red paint jobs.
Be sure to check out Bosque del Apache wildlife refuge to your south during the Spring or Fall migrations - spectacular!