Beware of cheap schools
What you must remember when looking on Amercian websites is what they don't say on them. There is a possibility that the tax isn't included in the quoted price. This is because all the state's have different tax rates so you apply the tax for whatever state you live in to the price. Some dont put the price of fuel on the quote either. Lastly, all the prices you see are based on you finishing in minimum time. Which rarely happens.
When you return you will have to sit the PPL exam just like everyone else and do a flight test. I can almost say for sure that a school wont let you near an ATO (the person you fly with who can give you an australian PPL) without doing at least 3 or 4 flights of 2 hours each to see where your "at" so to speak.
I would research this very carefully before buying a ticket to LA,SF or the like.