I'd usually use "queria um café" as a wish. If I am talkng to a friend, I would use it as "I wish a coffee". I'd never use it as a request, in which case I'd use "eu gostaria de um café" (I'd like a coffee). Therefore, in my opinion, your translation is not literal. But you have to consider that the use of polite expressions depend a lot of the social environment. So, many people might say "eu queria um café" or even the imperative "me traz um café" ("bring me some coffee") but in either way followed by a "por favor", as otherwise it would be unpolite.