And the second trick is, if you can use it there, how will the transaction be coded? Every credit card transaction has type a code that identifies the merchant type. It's the presence of this code that gets the transaction to report for the cashback bonus. I would not be confident of a foreign entity coding the same way.
But even if it does - you are still paying a 3% foreign transaction fee to use the card, so you are only gaining 2% cashback. Get a CapitalOne Mastercard, no foreign transaction fee and you can get this in either a 1.25 or 1.5 % cashback variety, without worrying about whether it will code right or whether it can even be used, or whether you exceed the bonus limit for the period. It's been reported here before that Discover is of limited acceptance overseas.