Houston, definitely.
But looking at the interstate map, when they leave Phoenix they’ll take I10 to Las Cruces (looks like a stop there) and El Paso, then continue on I10 through Fort Stockton to San Antonio and Houston. I’m basing this on where Prada and Marfa are located on the map which are below the route line. When they confirm the actual stops, that could change.
They’re definitely passing close, regardless!
Fort Stockton is about 70 miles from Alpine.