Elmer's Tacos joint has good Mexican food, but does not come close to being the best around the area. While the food does carry that authentic taste, quite a few dishes are...well, weird tasting.
I would recommend the hard shelled tacos. You can never go wrong with tacos, and for the most part this is the pretty tasty.
There are some other worthy Mexican food places to try when in Chandler, but Elmers is worth it if looking for a quick Mexi-food fix.