Correct...those locals would be calling your home phone so that would't be a good thing...good point and even the backup international plan wouldn't be appropriate. Works for you and you fellow countrymen but not for residents of the country you are in.

Most of the phones in the homes/apts we rent in France have internet calling as their regular home phone plan (i.e Orange) and free calls to USA are included in the fee. BUT this is country/location specific and not applicable to SXM or anywhere in the Caribbean that I know of.

But unless a vacationer routinely gets calls from the locals then wifi calling is great. I would just give out the resort unit phone number of where I am staying and let them call that number...return call can be made over wifi.