Ft. Bliss has a RV park but it is a bit off of the Interstate using US 54 or the 375 loop to access. Besides the one mentioned at Davis Monthon in Tucson there is one at Yuma Army depot also but it is pretty small and this time of year is likely full. Davis Monthon has lots of overflow spots if you do not need full hookups. How far do you drive in a day? Are you using I-20 from Nacagodoches or I-10 to go west?
I suggest this
Military RV sites if you are not already familiar with it.
BTW: there is a RV park at VADO, NM right at the 155 freeway exit just past the NM/TX state line. Western Skys RV park cheap, full hookups and fine for an overnight. Easier to get to and for one night as good and cheaper than Ft. Bliss. Across the freeway is a Chevron and a National Truck Stop (NTS) with as cheap a fuel as you will find in the area without driving way off of the freeway.
