How true this is I am not sure, but both our drivers (kuta locals) told us the safest machines to get your money out of is the BCA ATM machines. On JL Kartika, (near waterbom park) you will see a row of about 4-5 machines all in seperate booths.
He showed us the sign for BCA (its blue) and told us the other machines have problems and tourists often loose their cards ... never to be seen again.
We had no problems whatsoever using these machines, (we also used it outside the bali hai resort and spa where we were staying) although we were holding our breaths the first time.
You can only take 1,250,000 each day, but that is plenty =approx. $150
We took $1000 in cash and just used the machine on the last few days as a back up.
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We only changed our money at PT Central money changers. Got 6700rp. There is one at the enterance to Matahari supermarket section. The lady never minded at all that I stood there and counted 6.7 million rp. x 2. She gave me a receipt and all was correct. There are lots of PT Central money changers in Bali.
Another tip, and a method I have used before is putting money into envelopes for each day. Its no hassle at all and it was very handy. That way we didn't overspend and didn't run out!