I have been all over the world, I am not saying I am an expert on currency exchange but here are some quick tips.......
1) Try to stay away from the "exchange kiosks" at airports. Yes, some do give good rates but their fees can be really high.
2) If exchanging money at an "airport kiosk" always change the money AT the location you are visiting. Meaning if you were in Canada and traveling to say Australia, exchange the money in Australia, you almost always will get a better rate.
3) Contact your bank, they may give you a decent rate on English Pounds. If you give them 3 days notice they should have the English Pounds ready for you to pick up, but check the rate they are giving you first, and make sure they do not screw you with some "transaction fee".
4) Sometimes the best rate you can get is exchanging money at a casino. Casinos around the world usually have a great rate on currency exchange. For obvious reasons they want you with a wad of cash standing in their casino. Since you are going to Aruba, I bet you get a good rate on currency at one of the casinos there.
5) I usually use my debit card to get the locally currency, but before you do this, make sure you have at least one of the following on your debit card.......
If you have both, you are good to go throughout the world, if you have one, you should be ok, if you have none, then your debit card will be pretty much useless.
The way to avoid fees (don't have to pay an ATM fee) when using your debit card is to ask for "cashback". For example if I was in England I'd find a grocery store and buy 5 pound worth of food, then I ask for "cashback". Of course this doesn't always work, but some stores in England may give ya "150 pounds "cashback". You would pay zero fees and get the International banking rate on the currency exchange.
But as I said, that option doesn't always work.
If using an ATM throughout the world make sure you use one that is affiliated with a country's bank. The fees will be much lower. If you use some ATM that is sitting in a local bar the fees will kill ya. Also note that many ATM's throughout the world do not have the letters on the keypad. If your pin is "letters" make sure you know the "numbers".
Best place to find currency conversion.........
http://www.x-rates.com/calculator.html
Oh and if using a credit card out of the country, make sure you know the fees, credit card companies will screw you big time if you do not pay attention.
Have fun:SIB