When you're young and experimental, even if you have a steady girlfriend you're probably getting some on the side -- until you move in together and submit to terrifying exclusivity. Moving in and picking out curtains with the taco: Mercadito Cantina, opening Monday. With this slick, blonde-wooded sleeve, the lazy-namers behind Mercadito and Mercadito Grove have committed exclusively to their mainstay (the taco), while still trotting out brand-new permutations (when you're only sleeping with one food item the rest of your life, you gotta get creative). Twofer orders run the gamut from pollo (w/ tequila, lime, three-corn pico), to calamar (guajillo-battered calamari, orange pico de gallo, chile piquin), to estilo baja -- fish battered in Negra Modelo, so you and your meal can both drink like fish. MC also provides quarter- and half-kilos of meat (organic chicken, grass-fed beef, Berkshire pork) for make-your-own tacos -- an option known in Mexico as Taquiza, though to avoid any chance of association with Tequiza, they're thinking of renaming it "Steve".