Absolutely use either a debit card or ATM card. It is by far the easiest and cheapest way to get local currency. Once you get to the airport you should be able to find a machine and make a withdrawal. Also, that way you are carrying smaller amounts of cash and avoid the possibility of losing too much. I travel internationally all the time and do this in each country.

Some points to keep in mind with an ATM card that you may wish to check. First, make sure that you have a 4 digit PIN. Also, make sure that the account that you want to take cash from is your primary account. The German ATMs don't give international patrons a choice of Checking, Savings, etc. but always default to the primary account, which is normally your checking account. Also, see what their fees are for international withdrawals. Most US banks charge $3, but German banks don't charge, so that means you will be paying a total of $3 in fees every time you want local currency. If you are withdrawing $300 at a time that is a great rate, if you're withdrawing $50 ouch! There are also some US banks that don't charge at all if you're going to be doing extensive international travel it would be worthwhile to look for one of those.