Go to areas where the Americans go, don't get adventurous. Actually TJ is not that bad from personal experiences. Make sure you have a passport, don't drink the water unless bottled. Ice too. Be careful of back alleys and don't carry a knife, even a pocket knife. Stay with the crowds.
Don't drive...they will hit you on purpose!! Besides, you may make a wrong turn and they could kidnap you and anyone else with you and keep your car!! Not a good idea...stay in populated and touristy places!! Besides drinking the water and ice, you have to be careful about fruit and veggies that are washed in their water too. Only eat things with peelings and make sure you peeled the fruit yourself.