You’ve gotten the needed shots, the dog got his, too. You’ve saved the Starbucks pennies, packed the right clothes, you even made sure you have the right adapter for the your cell phone and MP3 player chargers. As the big day arrives, you’ll have to do a little homework in getting great currency exchange rates. The places to get the best rates are in banks, post offices and American Express offices, especially if you use Amex and bank checks and post office money orders.