You DID read about this a while ago; Judicial Watch published the item one year ago, in April 2015. The report received scant attention from the media (what a surprise). The few reporters who followed up on the story went to the usual suspects (DHS, DOJ) who assured them that ISIS is not operating a camp along the U.S.-Mexican border.
Here’s a blog post that provides a bit more detail:
http://formerspook.blogspot.com/2015/04/along-border.html
Judicial Watch actually posted claims about an ISIS camp opposite El Paso in the summer of 2014 and again last spring. The first report was followed by a flurry of increased security at Fort Bliss, the massive Army post in El Paso. However, the commanding general said the new security measures were not in response to an ISIS threat.
Spent a fair amount of time in El Paso on business in 2012 and 2013; Americans were advised exercise extreme caution when traveling south of the border in that area. Ciudad Juarez, the city on the Mexican side of the border, was long known as the “murder capital of the world,” and the State Department issued a travel warning for the city as recently as last year. Conditions in the city have supposedly improved, but I wouldn’t go there. In that environment, it would be easy for ISIS to set up shop and thrive.
One final note: when the first Judicial Watch report appeared almost two years ago, the FBI convened a meeting at the US consulate in Juarez, to coordinate expected media inquiries about the ISIS threat. If there was no local threat from the terror group, why hold a meeting?
But searching Google for it shows a number of sites have picked up the story today linking the JW story...including FoxNews. So I am thinking JW made a typo in their dateline.