As descendants of the Faithful of Númenor, we have inherited their tendancy toward the Sindarin tongue amongst ourselves. The practical end of this enables us to communicate freely with the Elves of Imladris, where we often mingle and rest from our journeys.
In the past, it had been mistaken assumed that Rangers spoke to one another in Adúnaic. This is bad form. We do no actively speak this tongue; any Adúnaic proficiency we have is tied mostly to the reading of old Númenorean documents. If someone from another culture should ICly address you in Adúnaic, it's often best to OOCly remind them that our actual native tongue is Sindarin.