As they said. If you have broadband access, but no SMTP connection to send mail, use webmail.
Alternatively, you may find that your Australian ISP has a "login" type SMTP server: if it needs an ID and password before you can send mail when you're at home, there's a good chance you can use exactly the same in the USA. My new UK ISP does that.
Before I had that facility, I bought $10 worth of Maglobe credit before each trip, and used that. It worked just fine. The package includes dial-in Internet access and e-mail from anywhere in the USA for the price of a local call. I could even send via Maglobe's "login" SMTP server from hotel broadband and the like - and it didn't charge me for that.
I've noticed more recently that Maglobe has got itself blacklisted a few times for handling Spam, so it may not be as useful as it used to be.