What you've seen on TV is bad, but not all of Mexico is like that. Generally the violence and murders are confined to drug gangs fighting each other and law enforcement. It's true, occasionally truly innocent by-standers are caught in the crossfire. Very rarely that's foreign visitors.
The most dangerous places are along the US-Mexico border where the drug gangs run their contraband into the US. The further away from the border area the better. Especially because sometimes there are roadblocks and hijackings of foreigner's vehicles.
I don't have any information on the town you are planning to visit, but you are heading into a province where there is a high degree of narco-crime.
You should read the State Department's latest travel warning http://travel.state.gov/travel/cis_pa_tw/tw/tw_5815.html
but remember it paints a "worst case" scenario.
You are relatively unlikely to encounter trouble as long as you stay away from drugs and stay out of trouble, but it sounds like you're going to need to be cautious about where and when you travel.
If you can afford it, consider going to one of the established resort areas such as Cancun, Puerto Vallarta or Merida which are free of this type of crime.
Phil from the safety hub almost 7 years ago