Did you ever mention whether you were fair complected or dark complected and what your history of sensitivity to the sun has been up until now? The sun in Cancun can be positively brutal if you're not prepared for it and can put you out of commission in a single afternoon (without you being aware until it's happened). Unless you're going there specifically to get sun (and a lot of it), you may want to start conservatively and work your way towards the tan you want. In Cancun, you can ALWAYS get enough sun to quickly get a tan, but it still takes forever to overcome the effects of overexposure. Work to the wise - bring your own sun tan lotion. The price of suntan lotion is about 2-3x normal in Cancun.