Rosa Mexicano [1063 First Ave. (at 58th St.) 212-753-7407]
The guacamole is to die for at this trendy, upscale Mexican eatery. The rest of the food is delicious as well (and I recommend the trademark frozen pomegranate margarita as a drink). For main dishes, I was especially fond of the Enchiladas de Jaiba and Mixiote de Cordero (lamb shank presented in parchment paper). Let me warn you that this place is only open for dinner and is ALWAYS crowded (there are other locations on the Upper West Side and in the Union Square area).