Hey I just lived in Mexico from Dec to May of this year here is some intel that could probably help you out.
- If you see one or multiple males wearing nothing but Ed Hardy clothing, stay away and avoid them, they are likely cartel scouts
- Never drink tap water, buy the big jugs of water it is the best value
- If you go out and enjoy the night life, don't mention your affiliation with the US government and avoid guys who are surrounded by women way out of their league
- Keep an eye for males wearing rosarie bracelets, it is a cartel identifier
- Street tacos are the best, but not matter what you eat prepare to have the shits for several days on your first or second week, after that you will be good to go
- If you ever get pulled over by local police, it is customary in Mexico for you to get out of your car to greet them at the halfway point between the two vehicles.
- On occasion you may see random cones on the road with police vehicles off to the side, these are called "Retenes" and are sort of like DUI checkpoints but they are looking for drugs, be sure to cooperate if you get motioned over
That is all I could think of, stay safe, keep your eyes open and your SA on full blast and you should be good to go.