About 50% of Mexico is in fact a desert. But as you said, Mexico is huge and that still leaves 50%. I imagine the temperature in Mexico really depends on your elevation. If you are in flatter areas i would imagine it is much like Florida...or Vietnam. On the other hand, if you are in higher elevation areas, it is going to be cooler. I think the temp drops 3 to 6 degrees F for every 1,000 feet of elevation.