El Dorado taco shop is run by a great lady who cranks out great tasting tacos. They're about 3/4 blocks down from the beach on Calle 7 Sur.
Just around the corner from my place and where I often stop on the way home from diving. The flies can be a bit bothersome sometimes but she's got some tables outdoors now so that is better. The place across the street - La Casa de las Iguanas - has good food also. I've picked up takeout lunches there for $45 pesos (about $4 US). Or they will deliver for another 5 pesos. Open early and closes around 4.
FYI there`s another el Dorado on the island cross road up around 75th Ave or so. They make GREAT tacos. Place is always packed with locals.