It's gotten pretty severely unsafe. Most of the violence seems to be directly related to the drug and smuggling businesses, and those not involved in either generally aren't targets---but mistakes happen.
A friend of mine has family living there; a few months ago, they got up one morning to find that a body had been dumped on their front steps. It seems to have been just a mistake: someone wrote down an address wrong, or something, and the "warning" got delivered to the wrong house. (Good thing they didn't hear anything and go to the door to check it out.) It's probably not a good time to visit any of the border cities just now.