re: best place for margaritas in New Orleans?

Your house. Get some Agave nectar and a ton of limes. 2 parts tequila, 1 part lime juice, 1/2-3/4 part agave nectar.

This is how it's done at Tommy's Mexican restaurant in San Francisco, and it's hands down the best margarita you'll try. Put it in a shaker since the nectar doesn't want to dissolve. Tequila martini almost, but damn it's so darn good. Be prepared to get pie-eyed. I use Hornitos Reposado, but any GOOD (relative to wallet thickness) one will do.