There's Habaneros down the street on Sherman Plaza and then there's Mercado Juarez. The tacos are the best I have tasted in Madison so far. I have not been to Los Gemelos yet but I'll leave that to a future review. I ordered 4 tamales and a Carnitas for my brother and 2 Carnitas and 2 Pastors for me. The taco Pastors were bursting in flavors of awesomeness and the Carnitas were seasoned well. I haven't tasted the tamales myself but I recommend the Pastor if you can't make a decision and the Carnitas. The order comes with a side bowl of mild green sauce and the tacos come with limes. I like my tacos with cilantro and onions and make sure you get something to wash down those delicious tacos with. I usually get Jarritos Tamarindo soda though you might not like that flavor.
If you're confused where to order go to the cash register as that's where they take orders. They don't take orders at the meat counter so don't go over there. Don't forget the drinks!