300 rand? Thats a bit steep. Are you staying in a single room? Or a dorm?
Best thing to do is to take a bit of cash with you and leave your card at the backpackers.
One thing... Do NOT go to the atm if there is people hanging around. I can't remember how they do it but they freeze the atm and then tell you to type in some code. Then your pin. Then they will try and watch you to get your pin.