Assuming you own your home (rentals vary based upon your needs / wants):
Food: >$30 BZE per day, based upon your tastes, etc. If you cook at home / have cereal and maybe do one local meal per day out.
Alcohol: 1 bottle wine > BZE $30, rum is cheap and beer is $2.50 if you purchase directly (normally $5 or 6 each in a bar.
Groceries and toiletries are gonna hit you hard - at least double what you might pay in the states IF you can find it. The local products may be less, say, sugar, eggs, flour, tortillas and rice.
Golf cart rental: $600 US / month (if you live North of the bridge you might find that you need one - we did and the cost of owning verses rental is about the same). If you are in town, you may want a bike or use taxis when shopping.
Utilities: based upon where you are (well water, cistern or city), electricity is high and phone/ internet much higher than the states (plan for at least double). Cable is reasonable.
Other items (like hardware store or clothing) is much higher - maybe 3 times what I am used to paying and the quality is lower.
For many items you might find that shopping in Chetamul is worth the trip occasionally.
It is difficult to judge these costs as everyone has different tastes, but we have found that daily living expenses such as meals and utilities were much higher than the states, with housing costs about the same.
AmbergrisCaye.com 
