From Sint Marten the serving Inmarsat satellite (Inmarsat-4 F3 at 97.6°W) is actually located west by south (260°). Also the elevation angle is quite high there (45.5° which is halfway between the horizon and the zenith), so you don't need that much of a clear horizon to get a signal (calculate relative satellite positions at
http://www.dishpointer.com/).
As we are going a bit off-topic here, shouldn't we start a separate satellite phone thread?