You will get GPS signal almost anywhere in Australia but it depends on your surrounds, some are more sensitive then others and will get affected by trees, forests and mountains.
I would look at getting a Bluetooth GPS receiver like the QSTARZ BT-Q818X.
A friend has just bought one and it seems to be very very good, better then the Globestar BT-338 that a lot of people use.
We have a Garmin GPS-18 that is a USB type but we find the Bluetooth (BT-338 that we have) way is more reliable, easier to use once set up and more stable plus higher sensitivity.
The Bluetooth set up doesn't seem to loose com ports or drivers all the time.
With the QSTARZ BT-Q818X that a friend has it seems to be 10x better then the Garmin or Globestar with better fix time, sensitivity and accuracy.
The QSTARZ BT-Q818X has a new chip design and it has had rave reviews on the internet.
I would forget the USB style and go with the Bluetooth.
http://www.qstarz.com/Products/GPS%2...BT-Q818X-F.htm
The Qsarz Explore 2000 GPS seems to be very good value for money and we may end up with this one.
http://www.qstarz.com/Products/GPS%2...BT-Q2000-F.htm
Both are under $200.00 AD.