Well unfortunately you are heading to southern Australia in winter, so it does cool down and the bite slow. Freshwater flyfishing will be out but you might be able to chase Australian salmon (a perch species not a salmonid) etc along the South Australian Coast.
Im not all that certain of South Oz fishing as never fished there.
Im an Australian but from Tasmania.
Personally if I was travelling that far and wanted some really decent fly fishing Id head north into the warmer parts. Easiest to get to from Sough Auistralia would be a flight (or thetrain if you into looking around, stop off at Uluru), due north from Adelaide to Darwin. You will arrive there in a good time for chasing barramundi in the fresh and saltwater, although it can be windy. They are a bigger,stronger relative of the snook that jump well and can be taken on flies, lures and bait. Hell of a fish. I attached a pic of a nice lure caught one, not mine though. One day!!!
If you want some advice from a local email guide Grant Hatcher, with a few ideas on what sort of fishing you like, any species etc and Im sure he'll give you "the drum" on the best action etc as we say down under,
mthatch@ozemail.com.au
There might also be queenfish on the chew (big silver fast and take a fly readily and jump a lot and one I really want to catch) maybe threadfin salmon, in the estuaries and the pelagics like spanish mackeral and longtail tuna may be in Darwin Harbour on the neap tides if you dead set on the salt.
You can grab all the details on the Northern Territory at
www.fishingtheterritory.com including checking out the individual game species available, many of which you won't have heard of but pull like a train.
Other things not to miss Down Under
If you get to Darwin try the mud crabs _ sensational
Try James Boags Beer _ best in the world out of a longneck or Cascade Pale Ale draft best "off the wood"
While your in Adelaide go to an Australian Rules football game _ and support a Victorian team, you'll make lots of friends hahahaha. Eat a meat pie and local Coopers beer. Our version of a hot dog and beer at the baseball.
If you fly in through Sydney you can also try your luck on the local saltwater scene there including yellowtail in the harbour.
If you still want more info, and maybe a fishing buddy or two log onto
www.flylife.com.au _ the best fly fishing magazine in Oz or the flyfishing bulletin board at
www.sportfish.com.au
Hope it helps,
Anyone else interested in Australian information only too glad to help. Some fantastic fishing from trout to marlin available at different times of the year Down Under and compared to the US very few fly fishers. Post or email me
Cheers Steve D