On the north side of Jean Talon with entrances from both Place du Marche and Jean Talon, El Rey del Taco is definitely the best place I've found in the area for Mexican. The pork tacos are spicy and delicious, the mixed meat plate is a yummy mountain, piled with steak, sausage, pork, rice, spicy meat sauce, sour cream and more. The nachos are tasty but at 15$ they are overpriced and out of synch with the rest of the pricing on the menu. The staff are super funny and nice and they have a sign up declaring their intention to be a business with happy customers that's a great place to work (a-dorable.)
El Rey is too brightly lit for me to love eating-in here for dinner so we usually do takeout, although as an afternoon stop during market shopping it's excellent. The resto doubles as a specialty shop full of Mexican products - foods, shampoos and other imported brands. They also sell homemade salsa and guacamole from a fridge in the back - the verde is insanely firey and delicious.