You can also take Alaska Airlines from Vancouver to LAX non-stop. From there you can take Delta non-stop into Belize City.
Also, American Airlines has a one-way special from LAX to Cancun for only $175!
Spirit Airlines just sent out specials of $.01 each way from LAX to Guatemala City. I think you have to go through Ft Lauderdale, though, their hub, which can make for a cheap, but VERY long day!
Just an idea....