Cancún has a reputation for being safe, and the Zona Hotelera is particularly well policed and secure; however, it is always best not to leave valuables unattended in your hotel room or beside your beach towel.
Vehicular traffic on Blvd Kukulcán, particularly as it passes between the malls, bars and discotheques at Punta Cancún, is a serious concern. Drivers (often drunk) hit pedestrians (often drunk) on a frighteningly regular basis along this stretch.
Swimmers should also be aware of the potential danger of powerful undertows on the eastern beaches. Look for the colored signs before you swim, particularly on Playa Delfines and Playa Chac-Mool.