Signal is where Ennis and Jack met Aguirre to stage the sheep herds and truck them up to the trailhead on Brokeback Mountain. Ennis is originally from Sage, in the southwest corner of Wyoming, a rural town.
Riverton is not far from where the mythical Signal is, and Dubois is one of the towns they ate at between Signal and Brokeback. My best guess of the description is that Brokeback Mountain is supposedly in the northwest Wind River Range, which is just southeast of the Tetons. If you look through our messages or search for Dubois, which is where some of the scenes in "The Long Way Home" occur, Dubois is about 80 miles from Riverton northwest, and is on the verge of the Wind River range.