I haven't been thrilled by any of the places on 46th Street. I'd highly recommend traveling out to Astoria for Malagueta (I think they serve the Baiano classic Vatapa, but most Brazilian places seem to). The food is excellent, the staff very friendly, and it's a cozy little place.
I suggest Via Brasil at 46th Street. The food is really good and very authentic. The menu is pretty much what you would get in a restaurant in Brazil. I go there whenever I am homesick. I don't lke the decor, though.
Delicia in the West Village is also very good, but the service is REALLY slow. If you have the patient to wait a long time for your food it is a good option.
Zebu Grill in the Upper East Side is another good option, but they have a limited menu, that's why I prefer Via Brasil.
I went to Malagueta a couple of times and the food is very good, but they adapt a lot to the "gringo" taste, they put hot pepper in many dishes. In Brazil the pepper comes at the side, so you add to your taste. I could never eat the moqueca there exactly because it has so much pepper.
There is no restaurant in NYC that specializes in Bahian food. However most have moqueca.
So I recommend:
1. Via Brasil
2. Zebu Grill
Both excellent w/ good caipirinhas
3. Malaqueta, also excellent if you want to travel to Queens
I would avoid Plataforma--an expensive tourist trap although the food is good.
Modt waitpersons in all three plces are Brazilian and hence speak Portuguese!
September 2nd is the annual Brasil Day Celebration in honor of Sete de Setembro (7th of September, Brazilian Independence Day). All around the 46th street area there will be tons of street vendors selling Brazilian food, including baianas making acaraje! You're sure to find tons of Brazilians there, along with awesome food and tons of samba...