International Marriotts Also
Ritz Carlton's not accepting Marriott cards is a high class problem. I have been to many Full Service Marriotts and JW Hotels outside of the US and they treat gift cards like confederate dollars. They get nasty and shove you out the door when you insist.
It would be nice if Marriott Concierge or Socrates could post definitive instructions beyond "look it up on the portal"