We've been going to Salvadorean-cuisine (mostly) ABI Azteca Restaurant for years - 3005 Columbia Pike, Arlington - and always enjoyed our meal. One of the few "hole in the wall" ethnic places my wife enjoys. It's got a "neighborhood" atmosphere, and the service is always outstanding. Plus you can spend an hour studying their collection of hats-of-all-nations on the wall.
Pupusas are generally excellent, tacos and burritos and enchiladas pretty good, meats OK, tamales not to my taste, lunch specials are incredible bargains.
But tonight I ordered this and that so I could "graze" lightly, and found a soft taco of beef tongue that sent me to heaven! Moist (too much so to be a handheld item), tender, well-spiced, generous at $2.50 each, and accompanied with a tiny saucer of optional orange assertively-hot sauce. Ask for some curtido on the side as a crisp clean accompaniment to cut the rich flavor. Beer is also a good accompaniment.
The rest of my meal: a plate of frijoles refritos and a generously-sized sweet corn "tamal de elote".
This is one of my "I'm never eating anything else again" discoveries.