There are 2 species of tree common here with nearly identical flowers. This is either Beach hibiscus (Hibiscus tiliaceus) or Rosewood (Thespesia populnea). It is my understanding that the Rosewood tree has more elongate leaves, whereas the Beach hibiscus leaves are more round (being about as broad as they are "long." Given that, I think this is Beach hibiscus.
From BIRD ISLAND NOVEMBER AND DECEMBER 2009