It depends on the resort. Their rates pages should say, most use US$.
Article Number: 386
Author: Mon, Aug 17, 2015
Last Updated: Mon, Aug 17, 2015
Author: Marty Casado
Online URL: https://ambergriscaye.com/help/article/when-i-am-looking-at-lodging-rates-on-the-internet-are-they-in-belizean-dollars-or-american-dollars-386.html