There is a two-block stretch of Lexington Avenue in the low 100s that's filled with charming little dining establishments; one of them is Itzocán Bistro, which promises and delivers Franco-Mexican fare. True to its name, Itzocán is more of a bistro than a Mexican restaurant, and you won't find chips and salsa here. Rather, bread and butter are brought to the table. Mexican ingredients and flavors impart a lively, subtly assertive twist to a traditional French bistro repertoire of dishes, putting Itzocán Bistro in a class of its own. More