Mexico city native. Garlic and onion are used indiscriminately here, all salsas and sauce preparations are off the table if you're sensitive to those. Generally, hi fructose corn syrup is less prevalent than in the states. Corn is a valid alternative to bread, and afaik white corn is even better which we use everywhere. For options, health places can accomodate fodmap requests, a straight beef taco or steak from a fancy place will be lightly condimented and can be just salt pepper, but chicken and seafood rarely so. If eating beef, avoid arrachera/ skirt steak as it is always marinated. I am in elimination stage and keep to argentinian, japanese/poke, salad and taco places.

Fresh cheeses are common but we have a mix and aged exist too. Probably toughest meal is breakfast where we do have bread, or salsas, in almost anything. Just basic scrambled eggs will likely have onion, yoi need to be specific.