If you live in or near DC and you want a great place to go, try Oyamel in (the newly hip)Crystal City. This new restaurant is owned by the Jaleo people and is like Jaleo in that it's tapas, but this time Mexican. We went last night for NYEve and it was fabulous. We had pomegranate margaritas (though I skipped the crushed worm/chili salt rim. ICK!) and about 8 plates, including tilapia tacos, carnitas, a pretty red/green salad of tomato and cactus, snapper and even desert of chocolate flannish thingy with mole sauce. Some of it sounded odd on the menu, but was delicious.
[Side note: Oyamel is a big, beautiful glowing gold atrium - very glam, though you won't look as good in there as you will look at (sic) Rosa Mexicano! I have not been there to taste the food yet, but it sure is purty. These pictures don't do Rosa Mexicano justice at night when it is dark and glowing blue.I don't have any pix of Oyamel.]
In typical DC fashion, Oyamel does not take reservations. Here is a WaPo page on it, though Tom Sietsama's review is a little better than the 2/4 stars would suggest.