Sydney? great surfing and surrounded by national parks. Great Canyoning.
Melbourne? wonderful city also surrounded by many national parks.
Cairns and the far north? lots of beaches, rainforest and of course diving.
Perth? Most remote city on earth I believe! But the real Australia.
Mind you, where are you from? Australian outback can be a pretty unforgiving environment and a National Park here isn't like Europe. Just a huge expanse of wilderness - you really are on your own if something happens. about 8 years ago
I also recommend Tasmania - fantastic hiking, surf beaches on several coasts and beautiful surroundings. It's a bit cold in winter but nowhere near as bad as Canada! :)
In terms of finding a job in Perth that's fun, I'm sure there are a number of adventure tourism businesses that you could check out. If you have any particular interests and skills (and first aid qualifications, probably) then I reckon you could find something by doing a bit of googling.
Failing that, Perth has lots of great bars and nightspots, so if you're into hospitality this might be a good way to meet people and make some cash. about 8 years ago