As far as Belize goes, I believe the Belize dollar is fixed to the US Dollar at 2 to 1. And I didn’t find anywhere in San Pedro last week that won’t take US dollars, but expect change in Belizean currency.
As far as charges go, I find that my Capital One Card has very good rates and is a card I only use on international trips. That way if something happens and the numbers are stolen, I just cancel that card and it doesn’t effect my other accounts.