Hello Helenmw,
Welcome to the Mattress Forum! 
The better options or possibilities I’m aware of in the general Ft Lauderdale / Miami / Palm Beach Gardens areas (subject to making sure that any mattress you are considering meets your criteria and the quality/value guidelines here ) are listed in post #2 here. The better options and possibilities I’m aware of in the Stuart / West Palm Beach areas are listed in post #2 here . There is some overlap between the lists and without knowing your exact location some of these may still be quite a drive for you. The largest selection is obviously in Palm Beach County along the coast, moving south.
Please let me know if you come up with any more specific questions.
Phoenix