Nope!
The island uses US dollars.
Domestic travelers are not required to provide proof of vaccination or a negative covid test prior to arriving on the island. Info at: https://www.discoverpuertorico.com/info/travel-guidelines
No. PR is still US territory so that is unnecessary.
PR is nice and hot, we would love for our guests to wear clothing that is both comfortable and breathable! Preferably collared shirts, no jeans please.