While the film doesn't specifically feature a translator, the characters of Cinque and the other Mende captives in the film are understood to have spoken Mende, a language spoken in Sierra Leone. The film uses subtitles to translate their dialogue for the audience.
It's important to note that the film, while inspired by real events, takes creative liberties with the story. The true account of the Amistad and the subsequent legal battles is a complex one, and there are many different perspectives and interpretations of the events.