Try and get away from the billed in USD but paid in IDR cash thing. Most of the operators doing this will give you a poor off-market rate to convert their USD billed charges. You can obviously circumvent this by paying them in USD but then you would be needlessly converting your AUD into a 3rd currency and layering up your forex and conversion commission losses.
I have heard stories of some hotel operators billing in USD but then refusing payment offered in USD and subsequently demanding a payment in IDR by cash or credit card after applying an absurdly disproportionate currency conversion rate.
This USD billing thing is an artefact and really not much more than a skimming opportunity. Unless it is offered sincerely offered to customers as 'service' to travellers carrying USD and seeking to settle their bill in that currency, if not then it is hard to view this as other than a simple scam.
If someone has booked from the US, sought a USD price or asked to settle in USD currency then all well and good, if the provider chooses to offer that service for US or other visitors then they should be applauded. Some providers may also do this with AUD or SGD as well, that is a service.
However the country is Indonesia, they have a quite stable currency and the IDR is normally used for everyday transactions other than some international trading settlements. There is no need for people to be billing, paying or converting unnecessarily to-and-fro into the currency of the United States of America for domestic goods or services, including accommodation services. Even the long standing problem of ex-Indonesian airline ticketing payment being billed in USD is finally breaking down. International airline ticketing is different issue though and this post is about accommodation billing.
If a domestic supplier absolutely refuses to bill in the currency of the Republic of Indonesia without playing disadvantageous forex games then maybe you should look elsewhere for an accommodation provider.
Edited: 12:38 am, March 25, 2011