I arrived in Brisbane late July 2009, chilly nights but 25+ through the day, beautiful!
Ended up in Canada as I couldn't work out immigration in Aus. Still trying to get over your way as it is the best living in the world.
Fly to Sydney, spend 4-5 days there (personally, I didn't like the place and wouldn't spend more than 2 days there), rent a camper and work your way up to Port Douglas/Cape Tribulation over the month.
Some spots to stop-over: Byron Bay, Noosa, Rainbow Beach, Fraser Island, Hervey Bay, Agnes...