Alright, you've decided it's time to stop wasting time at your current job and come to Caye Caulker. The only site you should ever use to purchase a flight is Google Flights. If you keep an eye on prices you can manage to get a round trip from the US or Canada for under $500, and if you're feeling adventurous you can purchase a one way for around $250. Check out my travel hack for getting flights for next to nothing. Your taxi from the airport to the ferry will cost $25 US or 50 BZD not including a tip. You can try to bargain but no legitimate taxi driver will take you for less..I've tried. The cheapest ferry is Ocean Ferry Belize  at $12 US one way or $22 US round trip. That's it, and since English is the primary language, getting to Caye Caulker couldn't be any easier.