They do have hockey there and they are generally happy to get Canadians. I played in Brisbane so can only comment about the situation there but where I was they had four tiers from beginner to advanced so I imagine it would be similar in Sydney. Have a look here and see what you can find out:
http://www.nswicehockey.com.au/If you click on the tab that says clubs (top left) you'll find more places to play in NSW.
Oh, and make sure to bring any and all hockey equipment and sticks you think you'll need, it's really, really expensive over there. One roll of hockey tape was $7 while I was there so I always made sure to stock up on hockey stuff when we visited Canada. If you don't believe me you can check out some prices here:
http://www.armoursmith.com.au/