Jon, one other thing to keep in mind is that your in-camera meter can actually help in this situation. Get close enough to shoot the full background, then place the subject in front and meter just the subject, same exposure? If so, look for another background, lighting or subject. With the darker skin tones you have described, try several filters. The green may or may not give sufficient separation of brown tones with this skin and sun.
This happens a surprising amount with objects against a clear blue sky here in the southwest. Ev of the sky can be about 14 1/3 without clouds, so can an object against the sky. While we see color as a division between values, the film may not! Filters are the best thing to change easily. tim
P.S. Sheet film really helps in this situation.