I just got back from fishing for 10 days in that very area - the upper Red, the Costilla, the Cimarron, the lower Rio Hondo. The fishing was terrific. The Red and the Hondo have more water in them this year than in any of the last 20 years that I've been fishing there due to the exceptional snowfall and runoff. The Costilla and the Cimarron were also running better than for a while. They're finally letting some water out of Eagle Nest Lake and Costilla Resv.
Size 12-14 Stimulators in yellow and orange worked great, as did size 14-16 Elk Hairs in olive or tan. Beadhead flashback PT's in sizes 14-18 worked well as a dropper along with caddis pupa in olive and creme in sizes 16-18. Honestly, it really didn't matter all that much what dropper you used. They were hungry.
The cutts in the Costilla were bigger on average than in previous years. Caught alot in the 16 inch range. They hit about anything but they hit them quick so be ready. Stimulators are always good up there.
The upper Red (in the upper canyon above the town of Red River all the way to the end of the paved road and on up) was also terrific. Caught many more browns this year than normally up there. Cased caddis were thick under the rocks and in the vegetation. Also...if you fish the upper Red in the evening be sure to have something big, bushy, and white. The pine moths were everywhere. I just used a plain white Elk Hair Caddis in size 12 and it ate them up.
Good luck and be prepared for rain and sleet. Coming out of the Rio Hondo canyon one evening we saw a double rainbow that went from horizon to horizon. It was incredible.
Wish I was going back (or still there).
Joe