Coke and Pepsi can both be found on the island but seems to me like Coke was more common.
Forget the travelers checks, they are a pain. There are several ATM's on the island where you can get either Guilders or Dollars. I have heard of some banks charging a fee to use the ATM's but Wachovia has never charged me. A couple of currency notes, the Guilder is worth about $0.56. As a rough calc I use 2Nfl=1USD (Nfl is the most common abev for Netherlands Antellies Florin which is another name for the Guilder). While most places take USDs, your change will be in guilders. When adding up your change, pay close attention to the coins as there are 5 and 2 guilder coins that look a lot alike. It has been my experience that it's very unlikely that anyone will cheat you, however it is easy to assume that you were if you don't pay close attention to the coins (been there- done that, was sure glad I did not make a fuss
) Avoid taking large bills, many places can't handle $100's or $50s. I usually take several hundered in $20, use my credit card for larger bills and visit the ATM a time or 2 for the cash I need.
Most any dive on Bonaire is fine to start out on but you will be required to do a "checkout" dive at the site used by your dive shop. This dive is unsupervised and is intended to be a tune up/weight check dive. I have at least 120 dives on Bonaire and 99% of them are 40 ft or less. 200ft+ is possible but why, most of the life and color is 40 ft or less. I typically make 2 "deep" dive when on Bonaire, the double reef at Alice in Wonderland and the Hilma Hooker, both are at about 100ft. For a couple of very easy entry dives to start off with I would suggest Old Blue (up north) and Windsock. Both have very easy, sandy entry points. 1000 Steps is also very good if you don't mind carring tanks up 67 steps.
Can't help with the leagality of bringing back Cubans but if you want some, see Michel at "Chat and Browse" located near the Sand Dollar resort, he has them. He also has phones for calling back to the US and an Internet Cafe in you need/want to call or email back home. He can also transfer photos to CD's if you need that.
A couple of other thoughts, there is a $25/yr fee for diving on Bonaire (just upped from $10) , your dive op will tell you about it and there is a $20pp exit tax. You MUST pay the tax IN CASH before checking in with your airline or you will have to get out of line to do so, so be sure and pay the tax before getting in line(tax office located at the right end of the airport lobby). There is an ATM at the airport should you need last minute cash.
The food and water on Bonaire is very good, there is no problem drinking the water out of the tap and you should drink lots of it, as you will dehydrate quickly in the sun and wind. We buy a 1L bottle and refill it all week.
In restaruants on Bonaire it is considered rude to place the bill on the table of customers before they have ASK for it. This makes many Americans think the service is very slow. To ask for your bill, make eye contact with your server and jesture like your are "writing" on your hand, they will bring the bill.
Hope this helps, enjoy Bonaire.