Marco Polo  $$-$$$    (#7)
Pino Suárez 806, Centro
Daily except Tuesday: 8AM - 8PM.  Credit cards
This is one of the few seafood restaurants close to the city center (a 15-minute walk north of the zócalo), and one of the best of its kind. The typical Mexican-style fish and shellfish are attractively presented and tasty, and if you come expecting reliably well-prepared, if not gourmet, cuisine, you won't be disappointed. Dishes cooked in the adobe oven are especially worthwhile. The setting adds to your dining pleasure. Tables sit in a patio surrounded by a lush, tropical garden, providing a relaxing ambiance for a leisurely, delectable afternoon comida. A great place for breakfast too.  Tel: 514-4360

(Note: Another Marco Polo on Calle 5 de Mayo is of markedly lesser quality. Don't confuse them.) 
From pages 37-38 of Oaxaca Tips