I have a Visa, "hybrid" debit/credit card. Is there a way to make it act as a credit card by default so I don't have to hit "cancel" or "ok" when checking out, just to get it to use credit mode?
In those cases where the checkout boxes don't always ask (which many do), they typically ask based on the BIN (the first six digits, or really the second through sixth digit, which is the (formerly) Bank Identification Number, now called the IIN - Issuer Identification Number. It's not based on asking the bank and getting an answer, just based on a database they keep stored on the machine.
This means there isn't anything you can do to avoid this short of getting a credit card from your bank to use in place of the debit card. You might get a low limit credit card and pay it off constantly, for example.