I just got a Prius II yesterday, the sales guy only showed me the push button parking brake, should I also be setting the parking brake pedal whenever I park, or is that more like an emergency parking brake for hills?
The push button is Park in the automatic transmission, not any part of the brakes. The foot pedal is what you use every time to make sure your car does not roll away and hit someone.
The "P" button is not a "brake" as such. It is the same as the "P" position in any automatic transmission. The foot-operated pedal emergency brake is just that---an emergency brake. After I stop my car, I engage the "p" button, and turn off the power. I don't use the emergency brake, except when parking on a steep grade, just as insurance. If you do use the emergency brake, be sure to engage it all the way, so you don't forget and go driving off with it dragging.
The ECU will beep and complain at you if you drive with the emergency brake on. (I've accidentally done it before).
Like JimboPalmer says, I use it all the time - learned to drive that way. Exception to the rule - when it's wet out. You don't want the brake rusting itself to the drum or rotor.