I stopped believing that years ago and here's the latest reason why from http://www.insightcrime.org/news-analysis/how-the-zetas-tamed-central-americas-coyotes
Fernando described two routes. One of them began in Chiapas, where hundreds of thousands of migrants arrived each year after getting their legs wet crossing the Suchiate River that borders Guatemala
Yes that happens also—sometimes the coyotes leave the aliens in the Mexican Desert next to a mall in Chihuahua (that is very modern and looks better than anything El Paso or Tuscon has) and say—Bienvenido a los Estados Unidos!
Big deal...
The Mexican Army hunts down and robs, beats, imprisons, and sometimes kills their illegals.