Altitude is a significant factor in imaging Jupiter. That and seeing have major effects on your ability to get good data. That said, practice makes perfect, so if you don't have a lot of experience now is the time to start practicing. Jupiter will start rising again from next year with it peaking around 2017-2018. Saturn will be good this year and so too will Mars. Those are good targets and I am just waiting until both get higher to start my imaging program on both of those targets.
As to whether you can get good seeing in Sydney, there are several people who have obtained good images of Jupiter, Saturn and Mars from around Sydney. Mike Salway is one of them. Though Mike has not done much planetary imaging in recent years.
Still he has the runs on the board so perhaps ask him for advice on local conditions.
