We are going to Oz for the first time in June/July. Here's my comments based on a lot of research and zero experience:

- If your son is graduating this summer, realize that it's winter Down Under.

- MEL is more southerly than SYD so their winter weather is cooler. Go north to Cairns or into the Outback and weather will be more mild.

- Do you plan to visit only one city, or travel around the country? Australia is the size of the continental US and as diverse...desert, rainforest, cities, ranches, reefs, skiing, palm trees, camping, fine dining...all of these are options. Decide what you want to do and that will narrow down the places to go.

- Because of increased airline competition and capacity, Qantas has some great fares from LAX to either MEL or SYD. US$ 299 each way plus about $150 in taxes and fees. That is simply unprecedinted; you need to purchase tickets in the next few days. Check other airlines too. You can get from PHX-LAX for $50 or less each way (or drive).

- Fares within Australia are not too bad considering the distance. Virgin Blue, Jetstar, and Tiger are discount airlines that fly domestically.

Hope this helps!