Americas, Bel Air, Coronado, and J.M. Hanks would be the best of the bunch, I believe.
"State 5A contenders" might be generous. I think the highest finish by an EP band was 8th, by EP Coronado in 1998.
Also one in El Paso.
Yep, typically referred to as "Lubbock Coronado" and "EP Coronado" in statewide circles. I believe there are also Coronado High Schools in Arizona, Nevada, and California (at least).
On the larger point, one hopes that having Andre Feagin (SCV brass caption head) on staff at UTEP will help drum corp's long-term prospects in El Paso, though if he's touring with SCV, he's not exactly around to take care of all the logistics.