Intro to the Belize City International Airport;
and getting there and back without paying a lot.
The International airport is not all that large, so finding your way around should not be a problem. It is a rarity in having a restaurant with reasonably good food at not outrageous prices, so don't be afraid to arrive a bit early for takeoff. You can change money there, but if you have US dollars, you will find them readily usable.
Getting to and Fro
For getting out of the International airport, the taxis have it pretty well sewn up and last I was there (2004), it cost $20 to get into town. If you are like me, travel light and don't like to hang around, it is only about 2 miles to the highway where you can hop the next bus onward. On the other hand, you could ask others who waiting at the carousel for their luggage if they would like to share a cab into town. If you wait until in sight of the cabs, the drivers will seriously keep you from gathering with others.
I only flew out of BZE this last time and this option is new to me, so I don't know, but a person could ask the last cabbie in line how much to get a ride to the highway. He would not be losing much of a place in line and would have time. Also, if you see someone getting out of an arriving taxi there, that cabbie would be fair game.
In order to get to the International airport, go to the city bus station. Tell the cashier that you want to get on a bus to the airport crossroad. This will most likely be a ticket with Ladyville Transport, but if another bus is going before their next one, it won't cost much more. The Ladyville buses are blue-green and white and as of 2004 cost just $1.50 Belizean to go to anywhere in Ladyville from Belize City. Tell the driver that you want off at the airport junction. There is a large sign, so you would not be likely to miss it.
In February of 2004, I had planned to hike in, but when I got off the bus, there were two cabbies staking out the place and charging $6 BZ to take people the two miles in. Thus, a person can get there for $3.75 US instead of $20. Even if you pay for a cab to the bus station to begin with, you are still way ahead.