Here is the travel advisory for the state of Coahuila, which is the area you describe.
Travel AdvisoryJuly 16, 2018
Coahuila state – Level 3: Reconsider Travel
Reconsider travel due to crime. Violent crime is widespread. Local law enforcement has limited capability to prevent and respond to crime, particularly in the northern part of the state.
U.S. government employees are not permitted to travel in Coahuila state, with the exception of Saltillo, Bosques de Monterreal, and Parras de la Fuente. U.S. government employees can only travel to those cities using the most direct routes and maximizing the use of toll highways. Between 1 a.m. and 6 a.m., U.S. government employees must remain within Saltillo, Bosques de Monterreal, or Parras de la Fuente.
U.S. government employees are permitted to travel to Piedras Negras and Ciudad Acuna but they must travel to these cities from the United States only.
U.S. government employees are prohibited from patronizing adult clubs and gambling establishments in Coahuila.