That threads's closed but very interesting nonetheless.
Ive driven round ( or rather my friend did the driving, I was navigator ) most of the South West US, Arizona,Utah,New Mexico,Nevada and California, we spent 4 weeks there sleeping in cheapo motels and on the move every day. But we didn't stick to Route 66 at all, in fact the only bit of it we saw or were on was in Flagstaff, Arizona.
That Western Trip that was mentioned in the thread would deffo get my vote, Monument Valley and the Grand Canyon are SO worth seeing