For a start, given the fact that it was published in Melbourne, it'd hardly be surprising if Go Set's coverage tended to be Melbourne-centric, although there was significant coverage of the Sydney scene and, to a lesser extent, what was happening in Adelaide, Brisbane and Perth.
For some reason Tasmania seemed to be a pop music free zone apart from vaguely-remembered coverage of a Loved Ones tour that reached the wilds of Devonport and Launceston. Some things, like the story that someone stole Gerry Humphries' harmonica, just stick in your mind.
But in any case it was hard to escape the conclusion that Melbourne was where it was at (baby). If you were looking for a Sydney-centric world view there was the semi-glossy magazine Everybody's, which featured significant music content but wasn't strictly devoted to covering the pop scene.
A second factor in the case for Melbourne is the city's dominance of the pop music TV scene. While Sydney produced some significant music TV, Brian Henderson's Bandstand didn't exactly set the universe on fire and Donny Sutherland's Sounds (or whatever it was called) paled into insignificance beside the Melbourne-based Countdown.
Before Countdown there were various two-, three- and maybe even four-hour Saturday morning music shows with names like Kommotion! that featured live bands as well as whatever other musical content they could dig up to fill in the lengthy time slot.
Hughesy, due to the programming policies of Townsville's sole commercial TV station, never actually got to see those Saturday morning shows, but you could see what was coming up or what had just been) in the pages of Go Set.
While there were Sydney-based record labels (Albert Productions being the prime example) one definitely gets the impression that Melbourne was dominant on the label front as well.