I know some people who live in the Portland, Oregon area and I found out that Air Mexicana is offering a round trip ticket to Cancun for only about $198:00 round trip. With taxes the total is about $330:00.I understand you have to reserve your ticket before August 9th.
From Cancun you could take transportation that could take you to Belize or the closest area could be northern Ambergris Caye.
Anyway, hope this helps someone who may live in the Portland, Oregon area get to Ambergris Caye inexpensively.
Sincerely, El-777