For a fixed/permanent DX location, I would rather not be on a mountain-top or some other area where you would have a dial full of distant pests.
With a permanent location in mind, I would look for an area with well-rounded tropo and Es possibilities. I would choose a rural area in the Southern half of Alabama or Mississippi, or the Panhandle of Florida. Specifically, somewhere around Apalachicola, FL (with a bit of distance from the high power transmitters there) would be ideal. This area of the US has abudant tropo, its typical Es range is fairly heavily populated, and the band is not completely full.
For a great tropo location, the Southern Texas coast is great. There's lots of open spots in the band, and tons of tropo around the Gulf Coast, and even into the mid-Southern states.
For a great Es location, I would pick the Panhandle of Texas, or western Oklahoma/Kansas. This area has a fairly open band, and the heavily populated areas in the Midwest, Southeast, Mid-Atlantic, and Southwest are all within the prime Es range.