Isn't Panama generally considered to be in Central America? Perhaps I don't understand what you mean here.
Could they have self seeded there? It's possible. In fact, the more that I dig into the coconut problem, the more l learn about how much we don't know about their origins. It's extremely frustrating. At least everyone (most everyone, anyway) seems to agree that there are two distinct strains and that they grow by the ocean. Other than that, it's a mess. However, even if we write off the coconuts, we're still left with sweet potatoes crossing the Pacific no later than ~1000 AD, and possibly earlier. Those likely didn't float their way there, so someone made that journey.
Hey, with a bit of luck and the right weather, one could conceivably do it on an inner tube. I just wouldn't want to be the one picked for the job, and I certainly wouldn't try it with something valuable if there were any other options for securing said valuable.
You're closer to the problem than I am and have a better understanding of it, and I'm feeling too lazy to research the facts myself, but we ought to run this one down anyway just to tick the box off if nothing else: I know that hurricane season in the Atlantic is late summer and fall, and I know that the winters can make for some miserable storms as well in the north Atlantic. I also know that the Norse only sailed at certain times of the year and I think that they wrote that down in the Sagas, but I don't remember when or which and I can't be arsed to dig it up - but you very well may have done so already. What's the "safe" time of year to cross the Atlantic, and does this coincide with the alleged Templar journey? As a former sailor myself I'm ashamed to not know this, but I did all of my seafaring from the west coast and the furthest that I ever got to the Atlantic was the Persian Gulf.
This won't prove anything either way, but I'm curious.