Yikes- short notice!
In our area, not a ton of tropical fruitgrowers/farms. You will want to stop at the local stands- there is one on RT 187 right after the bridge as you get into Loiza. Coco frios!
But there are a few stands along RT 3 as you go east from RT 188.
For trees, head down to Caguas botanical garden- there is a seller there. Or just to see some things growing, the botanical gardens in SJ is ok (a couple interesting things). For fruit- Go to the Rio Piedras market/mercado to find some stuff to taste. The market in Santurce is smaller, not as much stuff.
Contact me, I have guests over Fr/Sat, but I may be able to have you over for a quick visit if you would like Sun or Mon. Not a ton of fruit to taste right now, but lots in flower or with little fruit sets.