Do not rent a car in Melbourne or Sydney cities. Rental and $$$ parking will be more than taxis.
Both cities have good public transport to popular tourist areas. (look a the sticky threads)
Take the train/bus to Bondi (
beach or
junction)
The
Great Ocean Road is south west of Melbourne. A too quick 1 day or a better 2 day trip.
The coastal route from Melbourne to Sydney is more interesting than the multi lane inland Hume highway. You saw the same inland area from the train. The coastal route 2 or 3 days. 2 days can be a little rushed.
Note that the first full week of November is
Melbourne Cup week.The Cup is run on the first Tuesday of November. Accommodation is limited that week.