-Do negotiate your taxi fare (or ask the driver to turn on the meter) before climbing in.
-Leave things like unnecessary credit cards and expensive jewelry at home.
-Bring a bank ATM card and not large amounts of cash.
-Use a money belt or concealed pouch for passport, cash and other valuables.
-A Tourist card is issued to you on the airplane before landing in Mexico. Upon arrival in Mexico, it will be validated by an Immigration Officer, with the number of days you are authorized to stay, usually between 30 and 90 days. You will need your tourist card to leave Mexico, so be careful not to lose it as it can be a real hassle to replace it.
-Don't drink tap water even if the hotel has a purified water system. Mexican bottled water is very cheap to buy.
-Be sure to use sunscreen, even on an overcast day.
-Do get a Mexico cell phone rental so you can stay in touch and coveniently get important information during your stay.