My brother and myself are planning on leaving the San Francisco area and riding down to Douglass Arizona in July and then getting on the highway 191 and taking it all the way North to Malta Montana
Alter your route a little to the west in Northern AZ to US163 to Monument Valley. Great stuff along the way on your route. Canyonlands, Arches, Flaming Gorge. +1 on the Tetons and Yellowstone. Take at least a couple of days to hang out in that area.