What I've heard from sailors is that it's easy to follow the coastal currents and winds south as far as Panama. But at that point, if you want to return north, you basically have to sail to Hawaii, and a lot of people aren't comfortable with that kind of prolonged open water sailing. So, yes, you can pick up a boat there cheap. But then what?
I had a childhood friend that wound up doing exactly that. Except when he got to Hawaii, he liked it so much he stayed! Still there, I think. But he was a Trust Fund Baby and really didn't need to work for a living.
As far as bringing a boat back from the Zone, if you can afford to buy with cash you can afford to ship it right back to Fort Lauderdale and plenty of commercial ships right there at the embarkation point. Buy, then fly home. Wait for your ship to literally come in.