Are there more HNers in Adelaide than I suspect?
I would have liked to have stayed in Adelaide, but from my own personal job search there were very few development jobs advertised in Adelaide and those that were tended to use old technologies (e.g., zero Python jobs advertised on seek.com.au in Adelaide vs. dozens in Sydney and Melbourne) and be government or defense related.
That said there are a few interesting companies and people in Adelaide that want to build some cool things, but in reality a lot of graduates and other skilled people move interstate, especially Melbourne or Sydney.