My advice would be to completely and totally avoid the deep south no matter what (I'm from there and speak from years of experience) and the really big cities (terrible traffic and crime).

Try to hit Boulder Colorado, no finer city in the world! The Grand Canyon, Yellowstone Park and Moab - plus most of the rest of Utah are awesome.

Drivers and store owners in Wyoming (except inside Yellownstone Park) seem to have a common, pathological dislike for all cyclists. Most of Arizona is great except for the heat in the mid-summer months. The mountainous parts of Montana and Colorado have spectacular scenery and generally very good roads and many of the campgrounds are not too overcrowded.

In my experience, absolutely the nicest, most friendly, most hospitable and helpful people all seem to live in Nebraska, especially along highway 6/34 and 136. Lots of flat, long, straight road sections there. The Nebraska drivers are the greatest too. I came across two dogs that essentially lived on the centerline of highway 136 and had been doing so for over 12 years!!! (I met their owner after trying to drag them off the road) Great camping sites too. Iowa is similar in many ways.

Hope this helps. Good luck and have a great trip!!