>>I know that my new phone number will be: 226-XXXX for local calls.
My question is about a call from the U.S. -- It used to be 011-501-26-XXXX. Do we add the "2" in there now? 011-501-226-XXXX?<<
Yes, starting May 1 you dial the country code plus all seven digits.
Fortunately for Ambergris Caye, most of the telephone number changes are logical, basically 26 was changed to 226. But in some other places around the country the numbers changed almost completely.