Having just coming back from SYD a few weeks ago, I can honestly tell you to get a phone card! That's the cheapest and best way to communicate back home to the US. We bought a $10AUD phone card and it seemed to have last forever. We actually had something like $7+ AUD dollars left on the card when we departed SYD. Shop around and you'll be fine. I found, too, that certain McDonald's has free wi-fi but I wouldn't necessarily count on it everywhere.