I went to Mexico for a 2 week Christmas holiday last year (2012/2013). I brought my DSLR with 3 lenses and a Mamiya 645 Pro with 2 lenses. All packed in a backpack as carry-on. We flew to Cancun and stayed in an apartment in Puerto Morelos, no resorts. No problems at all. We felt very safe at all times. The locals were very friendly. Some of my images in the gallery are from that trip. We did a similar trip around Christmas in 2009 but then we drove all around the Yucatan peninsula with a rental car and stayed in local hotels. Again no problems at all. There were many checkpoints by the police or military on the roads but they never gave us a hard time. We had a little party with a local family on the street of Palenque, drinking tequila, banging the Piñata and lighting some fireworks at midnight. Our biggest worry was the Topes, massive speedbumps that could easily wreck the car, specially when driving at night.
Have a nice trip!
Menno