Well, there's beginning to be more real Mexican food in many restaurants so hopefully you can find such food.. Contrary to popular belief, they don't eat everything rolled up in a tortilla and smothered in cheese. In fact, they rarely make anything remotely like what we think are enchiladas as baked casseroles really aren't in their repertoire. They call that Swiss style which is why you sometimes see Enchiladas Suizas on a menu. Usually they are chicken on our menus but the name is actually referring to the cheese & baking which is something they rarely do. Real enchiladas are tortillas dipped in enchilada sauce with a filling folded in half, not baked and probably served with a layer lettuce or pico degallo, avocado and some crumbled queso fresco. And Crema. If you don't eat dairy just ask for those to be left out.
I digress. They actually eat a lot of veggies, grilled or lightly pan fried meat, fish, soups, etc. Especially in the Southern & coastal areas. it's the border areas where they don't eat many vegetables & whose food influenced Tex Mex.
Anyway, even at Tex Mex, you can choose fajitas, sometimes veggie, shrimp or mushroom fajitas. Tortilla & other veggies or seafood soup
just ask for the fried tortillas on the side or to be omitted. Squeeze on some lime. Pozole if they have it. Spinach enchiladas. Fish tacos if they aren't fried.
At an Italian restaurant, it's basically the same. The soups or grilled meat & veggie dishes. If you eat pasta, then primavera.
At Asian restaurants, just watch out for the sauces. I think Southeast Asian restaurants are going to be your best bet for healthy. Thai & Vietnamese. Vietnamese is my favorite. Here in Houston there are a lot of Vietnamese/Cajun places. The boat people that settled here really took to the cajun & creole as they already had the French influence and they use so many of the same ingredients.