RickandJulie,
I wouldn’t worry too much about it until you are about two weeks away from your trip. The Sargassum comes and goes on a fairly regular basis over the last couple of years and even if it’s where you are, chances are pretty good you can find a beach on the diagonal other side of the island that will be good and sargassum free. Or at least, that’s usually been our experience.
We typically go in April/May and Nov./Dec. and it’s usually not a problem although there was that one late April trip……….OMgoodness. But we always found another option if our first choice wasn’t great.