I haven't done the Enchanted Circle Century, but I have done a couple of tours on part of your route. I went from Taos to Questa, and into Colorado. The Garapata Ridge is a steep but not long climb from the Taos side. Looks like you'll be coming in the opposite direction. Expect challenging and beautiful riding. You should be getting the very beginnings of the fall colors --temps probably in 70s, but be prepared for rain/snow, especially in the high country around Angel Fire and Bobcat Pass. I'll see if I can dig any more specifics up on the route. New Mexico rocks! Have fun!