I've had cashiers in Germany balk at my debit card because it says "Visa" on it and tell me "we only take EC" or sometimes even "we only take EC or Maestro". The joke is of course that EC hasn't existed since 2007 (when it was renamed to "girocard") and Maestro was discontinued by MasterCard, which is why many German banks replaced Maestro debit cards with Visa debit cards.

I wouldn't rely on cashiers to know more than just whether they take debit or credit.