Anybody who’s spent time in cities with large Mexican populations can tell you that D.C.’s brand of south-of-the-border cooking can induce more yawns than memories of Yucatán. Hyattsville’s La Sirenita, on the other hand, gives you what you want: It not only delivers good, cheap food (particularly to a part of Prince George’s County that has lots of the latter and little of the former), but it also nails the Mexican basics while serving up a few surprises. The storefront restaurant is strictly utilitarian, with telenovelas on the TVs and banda music on the jukebox. The largely Latino clientele is made up of folks looking for something cheap, tasty, and filling after knocking off work. Follow their lead: The dirt-cheap ($2) tacos have some heft and aren’t overcooked. Plus, you have plenty of options to choose from (chorizo, cesina, and barbacoa, among the usual suspects). As the name (and the mermaid décor) suggests, seafood plays a starring role at Javier and Eloisa Guzman’s place. Try the soups, which come in enormous bowls and are never stingy on shrimp.