There are some dealers who are automatons and will just fire away, no questions asked. Most, thankfully, have some idea what a BS player is doing and will ask a second time before dealing the card.
I've had it both ways when I somehow didn't realize what the upcard was and hit a stiff on a bust card. It's not their job to make sure you know what to do but it is a reasonable expectation that they know the correct play and figure that's what you'd want to do.
However, they always seem to ask a second or even a third time when I'm hitting my 13 or 14 vesus their 2 or 3, and really hesitate when it's against their 6.
paddy