ATMS normally will only go as far as 3 million rupiah about $300 USD, you can stick your card in numerous times to get more out but watch your bank fees.

I have only withdrawn money once or twice from an ATM - I tend to carry cash from home (australia) and change at a reputable money changer.

I try and use my American Express and Visa as often as possible - but there are lots of drivers and little outlets where cash is King 0 so you might need to carry travellers cheques or cash