I agree with the US 160 route from I-25. We go to that area every summer. I have only pulled the Monte as far as South Fork, but have driven on to Durango.
Two passes. North La Veta Pass shortly after leaving I-25. Fairly long, but not too hard of a pull.
Then Wolf Creek Pass after you go thru South Fork. Going west is easiest. Not bad going up, but much steeper on the west side of the pass going down. There is a snow shed as you near the top. Mind the speed signs when they say sharp curve ahead inside the snow shed. They mean it. And take it easy going down, about 8 miles of mostly 7% grade on the west side. Two lanes both directions most of the way down so you can take your time without holding up traffic. And they do have a couple of runaway truck ramps just in case you need them.
Drove the pass about 3 weeks ago and came up behind a truck pulling off at the bottom with smoke billowing out of the trailer brakes. Guess he forgot to downshift. Coming back, there was an SUV/TT broke down right in the middle of the road about halfway up and two more pulled off to the side appeared to be cooling down.
No problems after Wolf Creek Pass.