Submitting PCB artwork mirrored?

I've never subimitted a PCB for fabrication

I'm using sprint layout, do all the bottom layers and NC drill get submitted mirrored?

In my experience, NO it is not supposed to be mirrored.
However, ask your fab guy. They might expect it mirrored, he's the only one who knows.

I always make it a habit to write something on the PCB, anything that will make it obvious which way the artwork is being viewed. That and I usually give them everything, Gerber, drill files, drill list, etc, anything that makes their life easier. It helps when you have those little "emergency" orders and would like them to do you a favour.