I should have been more precise. It is the Everglades Wilderness
Waterway that stretches approximately 100 miles through the western
Everglades National Park. The trip should be 8 or 9 days with no
roads, stores, etc. along the route. The Florida Keys are 20 to 30
miles across Florida Bay but I don't know what the range of a cell
tower is. When I thru-hiked the Appalachian Trail a few years ago I
was able to get cell coverage on the peaks of most mountains.

I'm not ready to invest in a sat phone at this time but it may be an
option at some point.