The reason I suggest leaving with cash is because you never know what could happen - when we landed, we had problems getting our money, so having enough cash onhand to buy a calling card or whatever could be beneficial. Better safe than sorry. Even if you get a poor exchange rate (say 78 c to the dollar as opposed to 82 or something similiar) if you have like 100 USD that transfers into 78 Euro as opposed to 82, so yes, you lose a few bucks, but it's not as bad as everyone makes it out to be.
Go to your local bank if you have one, and see if they do currency exchanges. If they don't, as for a place/bank that does. In Europe, if you have
to do an exchange of currency, do go to a bank. The exchange rate still isn't perfect, but you get a much better one than at a currency exchange.
Definitely do it before you go and not like at the airport. Anywhere there's a lot of traffic - airports, train stations, tourist areas - the exchange rate is bad. So, as long as you have the time, do it before hand!
And it's always good to have some cashish on the plane for those "extras" (you can use currency from where you're leaving from or currency from or where you're going on planes). Mmmmm... beer... Unless you bring your own of course!