I will echo Andyf's advice.... The cash passport is a good idea. A few supermarkets do them here in UK. I used one with USD preloaded with funds. I don't know if I am allowed to mention the supermarket I used for my card? I wasn't charged to withdraw funds or purchase at local restaurants
I think it's best to use a travel card, but it's not such an issue to also use change. Ultimately you do not want to be in a situation where you find you cannot use your card in a certain back or cash machine whilst abroad, (was in the bank recently and a guy from Spain was not able to use his bank card at any cash point and was stuck without any money). Make sure you have change when you arrive, for any transport and meals, but use a card for the main duration? You want to see which Bank, or company, has the best exchange rate for dollars -snip-. I'm not sure quite how expensive it is out there, but I know it can be quite dear!
[ Edit: Sorry, no promos please. ]
You can't open a bank account if you don't live there.
Traveling in Australia is easy you just use the AMT machines, get yourself a current account that doesn't charge to take money out you'll then only pay commission to the bank you take it out of this will cut costs.
Also taking out from ATMs mean you have current currency rates (rates go up and down).
Get yourself a credit card, check out for the best deal some you will pay costs on purchasers some you won't (this is important) could cost quite a bit of money if you get the wrong one.
Pay the full amount of your purchases off by standing order each month(set this up before you set off) and you shouldn't have any interest to pay.
Most cc companies charge interest on withdrawal of cash (check this out) the one I use doesn't so long as you pay the full amount off at the end of the month. It's best not to withdraw from credit cards because generally they charge interest from the date of withdrawel.
Get down to a few banks and check out their charges for both debit and credit cards.
Use a money belt (although you will be searched when you go thru the x ray machine at the airport (it's not a problem).
Put in any money you are not using, tickets and passport when not in use.
I always wear zipped pocket trousers they are a god send, you can put all your loose money in etc.
In crowded places carry your light weight pack on your front.
The only times I have lost money etc was when we left some gear on the beach in Dominica and once in Ecuador I had a top stolen which I was carrying over a camera.
We have never lost anything of great value in all our years of traveling.
Oh and if you are going to do Internet banking DON'T use an Internet cafe you cannot be sure the line is secure. Use a 4 or 5* business section in a hotel, the chances are their line will be secure.
Oh forgot you can use the libraries for Internet banking the lines will be secure, they usually allow half an hour to an hour and there is a small charge, but best to be safe.
Halifax Clarity credit card is good. I have one and used it in Japan, Zimbabwe, France with no withdrawal charges but there is some small interest charged in pence though. However if u use it to purchase in shops etc u don't get charged as well. The rates u get are amazing, I remember when I used for purchase in USD the rates were 1.55 but was getting 1.62. Checking today's rate for AUD its about $1.39 to the £1 but I would get $1.45 if I was using it in Aus now.