Ft hood would likely be a no go and almost all the area around it is privetly owned ranch land. The hill country would be a great area but unless Ford is planning on buying land for this, the options are limited at best.
I don't know about flying but I could be tempted to drive to one far off. I'm in Texas, I've been off roading in Texas since I was young. It would be cool to go to Wyoming and give it a shot there. Especially tempting during the summer.
The middles of the circles seem to be about:
Needles, CA
Evanston, WY
Middletown, NY
Gatesville, TX
I doubt it'll be in those cities exactly. All have known trails nearby with the exception of Gatesville.
Map overlaid with the Off Rodeo bubbles. If I was a betting man I would say the locations will be:
Mohave valley
Moab
Somewhere just Southwest of Waco in the Texas hill country
Near Scranton, PA