My duaghter resting and thinking after a short hike to look into the Bighorn Canyon
While I have never failed to see wild(feral) horses in the national recreation area, the best place to find the horses is on dirt roads to the west, but they are very rough. Spring is the best time to see newborn foals and also to see stallions establishing dominance and their herds. The basin has not dried out yet, so there is more green than summer and fall.
I chose this picture of my daughter in front of the frozen Bighorn River to show how accessible the views are with a little hiking ( or right from the overlook area too). The Pryor Mountain wild horse range runs through the Bighorn Canyon NRA, so one can get photos of the wild horses in front of the canyon too.