Absolutely my favorite taco place anywhere. The tacos are delicious and huge. I don't know what they do to make the meat so tasty but it is amazing. I cannot stress enough that they are LARGE. 4 or 5 will fill up a big, hungry person. And the price cannot be beat.
Ask any cab driver in SMA where they make the best tacos. It's likely they will mention Santos shop. Can never be sure when it will be open, but it seems to only open after 7:30 pm and not every night. When you do get lucky enough to be there when it is open take pictures. It is amazing to see the many skills the cooks possess, lightening fast mid air onion chopping,too fast to see taco filling. We've never been there when any other gringos were there, so we feel like our behavior provides amusement for the regulars, in a friendly way.
I love this place.