Thank you, Ursula! (And everyone else that chimed in.) I believe we may have a winner.
When I think of Acacia, I always expect leaves typical of plants in the bean family. Now I have learned that the "leaves" of Acacia aulacocarpa (and many other Acacias) are not true leaves, but modified leaf petioles (phyllodes) which function as leaves. That explains the linear vein structure resembling a monocot.
Also, I have seen trees in bloom around the Naples area looking very much like Acacia aulacocarpa or Acacia auriculiformis, or something similar.
I can't be sure of exact species, but it doesn't really matter, as both listed are considered invasive in Florida, so whatever I have will be removed.
Thanks again. Good info to have while the trees are still small enough to be easily removed.
I'm marking this thread as solved.