How is Sydney Australia like?

Like I'm going there in a couple of weeks and I'm just thinking what it's like. I will be staying at Elanor Heights I think? And I'm only staying there for a week. People say there a lot of tourists and "Dangerous people". And umm my friends are also coming and they said that they will get drunk and stuff because some of my family lives in Sydney and they have been robbed couple times this year and I might be staying there instead of Elanor height. And can you tell me what good places there are besides Opera house, Luna Park, Aquarium, Tarronga Zoo, Aquatic Centre, Aquarium. And thanks :]