In reply to Archibald:
https://www.gov.uk/foreign-travel-advice/mexico/safety-and-security
"Drug-related violence is a particular problem in the northern states of Sonora, Chihuahua, Coahuila, Nuevo Leon, Tamaulipas, Sinaloa and Durango, and also in Guerrero, Jalisco, Michoacán and Nayarit. Armed clashes between security forces and drug groups can occur at any time without warning. You should exercise extreme caution outside of tourist areas in all of these states."