I would be surprised if ISIS had only one location. We know there are well over 35 training camps in use by other jihadi groups, though so far as I know no one has ever been allowed in them. Suffice it to say they are not earning their Boy scout merit badges there.
Logistically speaking, a camp in El Paso makes a lot of sense especially if one is planning to funnel people and supplies into the US. The border is not secure in any way so when the SHTF, it will get much worse as control of the border will most likely be given up to drug cartels, bandits, and other low life like jihadi groups. It makes living in TX a tenuous proposition at best, so any of you living in TX should give serious consideration to building as large a MAD group as possible. (Mutually assured defense)
For God, Family, Country, & Liberty!