Well, salad in the sense of green salad isn't a very Mexican sort of dish, so one has to adapt.
There is, of course, Caesar Cardini's classic Caesar Salad, made in Tijuana in days of yore, but somehow I suspect this isn't what you have in mind.
I would start with a basic green salad and add some classic Mexican raw vegetables, such as the ingredients of your basic salsas crudas and guacamole: tomato or tomatillo, white onion, fresh not-too-hot chiles (e.g. seeded poblanos), avocado cubes. Radish slices would be excellent. Maybe sear some fresh corn kernels blazing hot until golden, let cool, and add to the dressing. For the dressing, I'd make a rough vinaigrette with cilantro, lime juice, just a dab of mustard for stability, a dash of cumin (or better, toasted oregano), and some mild olive oil, then toss the corn in this (if using) and dress the salad.
You could certainly add various pickled vegetables, like nopales (nopal cactus pads), carrots, radishes, and so on. There are also lightly-cooked vegetables allowed to cool, including zucchini and other squashes, which you might toss over high heat with a little toasted oregano.
Remember that one of the great arts of a decent salad is to take things out. It's sort of like Coco Chanel: before you complete the dish, take something off. Keep it very simple, fresh, and seasonal. Just use things that come up a lot in Mexico, and you're fine.