In most cases, it's ATM's as long as your bank doesn't tack on hefty fees and you make larger widthdrawals if they do (doesn't make much sense to keep taking out $20 if they are putting a $5 fee on it when you can take out 400 for the same fee)

Airports are allmost always the worst places to get the best rate.

Depending on how much money you are talking about, it may not be worth it to search all over someplace for the best rate. Sure, you may save a few dollars, but it may be not worth it if it takes you all over someplace.