We've done both Phoenix to Van Horn (2012) and Phoenix to Fort Stockton (2014). Van Horn is about 525 miles, and as Michael said, Fort Stockton is another 120 miles. The choices are small in Balmorhea and a bit off of I-10, if I recall correctly. GLC suggests Motel 6, and I believe there is one in each Van Horn and Fort Stockton.
Van Horn doesn't have a whole lot of choice for places to eat, but there's fast food and a Denny's (on the east end of town). Fort Stockton has a bit more choice for places to eat, but their Motel 6 has NO CARPET on the floor. (Some folks like that, others don't.) I just had never seen a Motel 6 with bare wood floors and not indoor-outdoor carpeting. But that extra 2 hours between Van Horn and Fort Stockton is hard on you. We just came out of Tempe, actually (Elliott Rd), and it was a long 650 mile day with 2 changes of time zones. (Van Horn will also make you change from MST to CDT in summertime, but you also aren't on the road for the exta 2 hours.) Also in your pro-con between Van Horn and Fort Stockton is the fact that motels are slightly higher in price in Fort Stockton. That's because there's an oil boom and the places fill up with temporary workers -- and Motel 6 was a prime spot for workers to stay!
La Quinta Inns are decent and not too expensive -- we've stayed in them periodically!
Donna