The Terreiro de Jesus is a great place to sample the local cuisine from street stalls, served by Afro-Brazilian baianas in their traditional white dresses.
Salvador has its own cuisine. You'll see baianas de acarajé everywhere, usually dressed in white (the color of Iansă, goddess of the wind), tables spread with a spicy and exotic assortment of Bahia's own version of fast-food.
An acarajé is basically a deep-fried "bread" made from mashed beans from which the skins have been removed (reputedly feijăo fradinho -- black-eyed peas -- but in reality almost always the less expensive brown beans so ubiquitous in Bahia).
The mash is deep fried in dendé oil (derived from a nut found on the dendé palm) and the resulting acarajés are usually eaten accompanied by camarăo (small sundried shrimp), pimenta (hot pepper sauce), vatapá (a paste made from sundried shrimp, peanuts, cashews, coconut milk, and dendé), caruru (kind of an okra stew), and salada (or salad, usually just diced tomatoes). These "fillers" can be included or left off at will, and the camarăo will cost a little extra.
A variation on the acarajé is the abará. An abará is fundamentally the same as an acarajé except that rather than being deep-fried it is boiled in a banana leaf.
Not all acarajés are created equal, in that not all baianas are equally adept and conscientious cooks. Some are downright bad and their acarajés (and customers) likewise suffer. So if you don't know, it's a good idea to borrow from the seasoned highway traveller who dines at the truckstop with plenty of trucks parked outside: go to where the baianos are standing in line. One well-known baiana with a deserved reputation for excellent acarajés is Cira, in Itapoan.
If you're just looking for a meal, workingman's lunches are easy to find. Just about every bar on the street serves decent food at lunchtime. What you'll usually get is rice and beans, and chicken or beef, and maybe a salad. It's good to know that frango is chicken and carne is beef. Sometimes you'll see the word "bife"on the menu ("menu" is cardápio by the way; that's a good word to know), but in Portuguese it doesn't mean beef, it means that the meat is sliced.
Unless you are starving, or there are two of you and you want to share a meal, you should order a prato feito (often referred to by the initials PF ("pay-ehfee"). That means that the meal is served on one plate, rather than on several platters, although in practice it's common that a PF will be rice and beans on a plate, with meat and salad coming on little individual platters. One of these meals will set you back the sum of three or four reais (less than a couple of bucks).
Getting back to typically Bahian cuisine, and to the top of my (and almost everybody else's) list, there are a couple of dishes which you should definitely know about: moqueca and bobó. These are essentially the same except that bobó is thickened with the addition of mashed aipim (manioc). The flavor base of these two dishes is similar to the ingredients in acarajés, including the ubiquitous dendé and coconut milk. Bobós, muquecas, and most other traditional Bahian dishes are generally prepared and served in a bubbling panela de barro (clay pot).
The outlying districts have a good selection of restaurants; Chinese joints seem especially plentiful in Barra.
Yemanjá, Av. Otávio Mangabeira 9292, Pitubá (231-5570). A widely-recommended typical Bahian restaurant.
Maria Mata Mouro is one typical restaurant from Salvador, it is in Pelourinho near Sao Francisco church. The shrimp is the best meal from the city. The restaurant is small with twelve tables but the service is great
Churrascaria Ancoradouro -Twilight dining in Barra Avenida Sete de Setembro, no 11 - Orla
Salvador. Tel 071 264 5561. Local Cuisine
Bahiacafe.com in the Pelourinho area, has good food excellent coffee a decent internet connection. The juices are good too.