Yes. By means of signs a Plains Indian could communicate with a speaker whose language was unknown to him. Though communication by gesture is probably older than speech itself, no system has ever proved more versatile and expressive than that developed by the Plains Indians. This proved to be a vital tool as even different bands within the same nation, such as the Sioux, were often unable to discern each other's verbal language. The Sioux believed that the gift of sign language was an indication of God's favor. As 19th century Sioux chief iron Hawk, pointed out, while the Great spirit gave whites the power to read and write 'he gave Indians the power to talk with hands and arms." The universal sign Language of the plains tribes naturally focused on words that had the most importance to Plains life. Such words as buffalo (fingers over head to represent horns), bow (hands imitating holding a bow and drawing the string) and council (clenched fists touching) were vital to the interaction between the tribes.
Well Duh,They used many sign languages.They used it because they didn't all talk the same language.