A block west of the spiffier (and pricier) competition of La Bonita, La Sirenita presides, proudly unkempt, with perhaps the city's best burrito. Bow to the "Super B. Relleno Burrito" ($5). This hulking two-mealer is not for the faint of heart, but oh, is it good. Pick a meat to be rolled up with rice, pico de gallo, the eggy crunch of petite rellenos and refried beans that are responsible for the alchemy that occurs inside the tortilla. Opt for the crisp-fringed, juicy shredded pork of Sirenita's carnitas and you'll be fully entranced by the siren's song.