Call me radical - but what do people think about a trip to Williamstown in the second half of September then? There are some fab things to photograph there, especially with that giant partially-constructed warship there at the moment. Also, lots of cute Victorian architecture, grand seascapes and city skyline views, HMS Castlemaine, etc etc. Plus proximity to coffee AND fish and chips... that is all :-)
Urban, easy to get to, far more interesting than the botanical gardens.