I think your plan to rent a camper in NY and drive to SF is not really too good. Our Interstate Highway System forces you to drive on very boring highways, and that means you will be seeing very little of the countryside and none of the small towns enroute. I think it makes more sense to fly to the area of most interest and then rent a camper for a round trip of that area. If you're interested in the far West, fly to San Francisco or Las Vegas and start from there. Certainly the most beautiful areas are the mountains of Colorado/New Mexico, the Pacific Coast, the Southwest (AZ, NM & UT) and the Northwest (OR, WA & ID).
I have driven coast to coast, and there is really little to see between NY and Colorado other than mile after mile of highway. The Interstate system gives one little choice in routes to take these days.
[ Edit: Edited on 03-May-2010, at 10:29 by Daawgon ]