I haven't been to Mexico with our kids but took my daughter to India at 6 mos old. If you are really worried about the milk, you can buy Parmalat or Horizon or any of the shelf stable - ultra pasteurized milks. They won't harm your baby and taste normal. This isn't dry milk, it is just hyper pasteurized and hermetically packaged to be shelf stable- non refrigerated. Whole Foods sells these, I'd bet you could find them at Andronicos as well.
Regarding food, in general, if you eat safely - i.e. no salads only foods you can peel, boil or skin, no fish - you should have no issues. I say no fish at least in India, but you should probably be fine if you eat fish off the coast of Mexico.
At 14 mos, your baby would probably be excited to eat fresh mango, bananas, etc. And all of that is perfectly healthy and won't cause an upset stomach. If you are really nervous, pack baby food. Have fun!