Champion is right about the savings in cost, but I'm not convinced that going to muni necessarily saves time.
Details on cost and time - Five guys plus luggage = probably two taxis to Muni. Cost of that is $50 Bz per taxi plus tip. Taxi-travel time is 1/2 hour.
Flights from Muni are on a reservation basis and the flights fly on schedule. If you have a reservation and miss it you are not automatically rolled over to the next one as they do at International. The flights from International will wait for you and will make sure you get to the Caye regardless of other complications. If you arrive early enough in the day you can probably make the muni connection work, but with five people and little planes you could find that there are not so many seats available at the spur of the moment (if you miss your reservation and need to roll over to another flight). For experienced travelers to Belize none of this is such a big deal, but first time arrivals are more confusing.
For a first visit, and up on arrival I'd suggest the more expensive, but easier flight from International, and arranging the more colorful and cheaper way for your departure and future visits to the caye. You WILL be back !
Edited by Diane Campbell (07/06/10 09:50 PM)
Edit Reason: grammar and stuff