You'll probably have an easier time finding Coca-Cola products overseas... Pepsi isn't nearly as popular. I don't know what country you're heading to, but in many countries, Diet Coke is not called Diet Coke -- It's called Coca-Cola Light... so be sure to ask for a "Coca-Light."

I think it also tastes a little different... maybe they use a higher ratio of syrup/soda water? If that's the fact, remember that more syrup = more caffeine!!

Have fun!
~D