Who were Native American talkers?

The people who spoke the various and incredibly diverse Native American languages were pretty much everyone in the Americas prior to European colonization.

Thus, I'm assuming you mean WINDtalkers. In that case, the Wind Talkers were Navajo/Dineh tribesmen who had been recruited in order to speak in Navajo. They were assigned to various units in the Pacific Theatre and communicated orders and messages between units in Navajo in order to keep it secret from the Japanese. Unlike codes which are based on systems that can be easily decoded, there were no Japanese agents who spoke Navajo. They also had to invent many new Words for their language, such as "metal fish" for submarine. See the film with Nicholas Cage and Adam Beech - Wind Talkers.