Mexico is a big country and it's incredibly diverse, so violence along the US border won't have any effect on your visit to Mexico. Most of the violence that has taken place recently is due to conflicts between drug cartels and the Mexican authorities. As a tourist, you are in little danger of having trouble as long as you follow common sense safety precautions and don't get involved with drugs. Stay out of trouble and if you do run in to trouble all American phones have the Mexican 911 that is (066) for Police and (089) Federal Police..