No problem using Visa cards in ATMs any longer, however, in popular tourist areas, there is a danger of card skimming, particularly at stand-alone ATMs and those in mini-marts. Check the machine carefully before using. Search Google for videos on how to spot a skimmer on an ATM. A safer option is to only use ATMs inside banks.
Current exchange rates on the street can be found here. Updated every few hours during working hours.
http://balibestrate.com/