We've actually eaten at Restaurante El Delfin several times, and have been pleasantly surprised each and every time. They have a wide variety of seafood on the menu, all of which the chef is expert at preparing. The wait staff is very pleasant, very helpful, and willing to go way beyond just standing at the table and not caring... They actually went cheerfully to correct an order.
This means a lot. When a restaurant makes a small mistake on an order then their true spirit can be found in the way they respond to their error. They passed this test very well.
We ordered shrimp tostadas for only $20 pesos apiece (about $1.65 US) which came with a quarter pound of shrimp on each tostada, and for another $65 pesos (about $4.75 US), I got the Sopa de siete mariscos (seven seas soup) which was unbelievable. There was a crab on top of the soup (I will soon post photos of our meal) which was the first thing that grabbed my attention. After I devoured the crab, there were other equally delicious fishes and squid and octopus and a few vegetables, lightly seasoned with standard seafood seasoning... This is the best seafood soup I have ever had this far inland.
The place is small, there is an outdated Google photo of their location before the remodeling, which I intend to replace in a few days with recent photos, and will post here photos of the place and of the meal.
The good thing about this place is the eastward-facing front, which keeps it cool in the evenings. I do now know their hours, but you can get any info you want from them by phone.
Summary: Clean, good food, quiet atmosphere, seating for 30, low prices and delicious food.