Sun Bowl is a tough draw. I doubt we'd have more than 2-3K fans there. By car you are 7+ hrs from the large TX cities. You are 4-6 hrs from the large AZ cities. You have to fly in for most fans.
El Paso is under rated as there are some interesting sidetrips within a few hours drive but lacks a draw of FL, CA or even NC. We had at least 8K for UNLV but Vegas is a destination and folks had time to plan for good deals. El Paso with short term travel planning will be pricey and many will not go.
BTW, gave some more thought and I think we had likely at least 4K Cuse fans in Houston (Texas Bowl) back after the 2013 season.