This is really more of a backpacking forum, but I'll bite. Part of the answer depends on where you are staying. But in general, it is good to have a roomy sturdy tent, some sort of shade for the hot days, and I like to bring a large patch of fake lawn to put in front of the tent entrance to help keep the sand out. Even in the winter, there are some pretty warm days. It can be really windy so bring your sand spikes.

Some areas in Mexico have large numbers of stray dogs that have the busy campgrounds staked out. You are going to have to figure out your strategy for dealing with them; they will try to get into your tent at night to sleep with you. You could wake up in the middle of the night to your better half screaming about some strange animal in your tent. "Honey, its just a dog" may not work too well to calm her down (especially with the way some of these poor things look).