Cycling in Sydney Australia
I am surprised no one has replied yet. I live quite far away from there so I really don't know much. A lot of people ride down south though such as through Royal national park, so you should be able to find a club ride quite easily. I think DHBC have rides regularly through there but I think their rides start in the eastern suburbs.
DHBC does ride down that way but to ride in a bunch at that average speed we expect you to be a CA member. This will be the case with most bunch rides I expect.
Only group rides posted by SSCC etc specifically expect a current CA membership for safety and insurance :-)