Hi Goose,
A cab from the BZE International Airport to the Marine Terminal (Water Taxi) in the city is $35.00 BZ / $15.00 US..... a 1/2 hour ride.
The water taxi is $15.00 BZ / $7.50 US...... a 45 minute ride.
The boat trip is always an experience, however, the choice is yours.
Bicycle cart guys are usually at the dock to transport your luggage to your hotel... ask before hand 'how much' - Considering you and your luggage can ride on a Golf Cart (Taxi) for $5.00 BZ / $2.50 US, you wouldn't want to be paying more than that...but you need to have that clear before hand!... (Note

If you don't already know where you are going, they can be quite pursuasive trying to take you to a hotel that offers them commissions...
When flying into Caye Caulker, the airstrip is a wee bit 'out of town'.... Upon arrival, Pick up the 'complimentary' handset outside the Airline Offices for an automatic Taxi (Golf Cart) Operator..... They'll pick you up and take you where ever you need to go for $5.00 BZ / $2.50 US.
My suggestion: Fly into Caye Caulker ( if you can afford it ) and take the Boat when you leave.... Avoid the initial, getting there hassel..
Good luck,
Cheers!
Diane