I used to live in SMA,
Try Pegasso, one block off the square, great chili en nogada, best I have ever had.
Breakfast is one block off the square also Mama's.
If you really feel like shooting the works, $50 a person for the best food you have ever had in your life, from the square towards the Iron building, you will have to ask someone, no sign, small converted house ran by a gentleman from Spain, called Cartuja.
Any other questions, just ask.