as and the Gulf Cartel, battling over drug routes into the U.S. and a ballooning drug market within Mexico, the principal casualty, peace of mind.Bar owner Sergio Trevino runs La Tumba in Monterrey???s once-buzzing bar district.SERGIO TREVINO, Owner, La Tumba: (through translator): There used to be 90 places that offered all types of music, food, cafes.