US dollars are widely accepted. It's a good idea to have some travellers' cheques on hand, though cash will bring better exchange rates.
Credit cards are near useless outside the capital and a few major cities.
You should be able to get cash advances on credit cards at major banks, though the system has been known to break down and getting cash can take a day or so even when it's working. As banks are free to offer current market rates, there's no black market to speak of, and changing money on the street is likely to be an invitation to a rip-off. The other thing to remember is that in local, low-end bars and restaurants tipping isn't expected. Bargaining is common and expected. Lonely Planet Publications Pty. Ltd. All rights reserved.