We are gonna be there presidents week. Now my cousins are thinking of joining BUT they need solid wifi border to work remotely.
For a week.

Are their places/rentals that have solid consistent wifi? Or a way for me to check for them?

La Vista Beach wifi is now all but useless. Hearing crickets from management.

Flamingo had a very strong signal last May.

French side has fiber optic internet at most places now it seems, at least orient beach and such. Was strong enough to stream/skype/video calls if needed. Sometimes Airbnb will say if they have strong Wi-Fi in description.
https://www.airbnb.com/rooms/53771079?source_impression_id=p3_1644180476_94s49fzoZRZ%2F5ZiW
like this place says Wi-Fi 100Mbps, so pretty fast

Yes. Fiber in many places. But today there are outages on the Dutch side - not sure cause - but it affected Telem, Coral, Chippie, etc.

Update: LaVista is installing new equipment. Seems to be working very well My wife is a therapist and was able to have 1 hour sessions with clients using Google Duo.