Hi everyone,
My family (of 4) is thinking of renting a car to get from Sydney to Melbourne.
I was wondering if it is cheaper to make a rental car reservation from the U.S. or wait until we are in Sydney to do so.
Thanks in advance.

I don't know, but since this thread is sinking fast without a reply, I will make a guess (other more knowledgeable people can follow and disagree): wait until you get here. Then you can check a few companies to compare rates. If you tell us where in Sydney you are staying, we can direct you to some of the nearby rent-a-car offices to make comparisons easy.

Thanks for noticing that this thread was sinking fast. I went ahead and made a reservation with Avis....and was pleasantly surprised. No drop-off charge (picking up car at Sydney and dropping off at Melbourne) and only costs AUD$50 a day for the rental of an intermediate sized car with unlimited mileage. Budget Car rental had a drop-off charge of AUD$220!

does that include collision waver insurance??

This is the basic rate; so, does not include any extras.

Hi Byr,
CDW (Collision Damage Waiver) costs $25/day with Avis. Without it, you'll be up for A$2750 if you have a dingle, irrespective of fault, so you do need it. The $25/day reduces the CD to $350.
HOWEVER, your Travel Insurance policy might cover it. If so, just make sure you have a copy of the wording to give to Avis when you rent. You would need to verify that it covers the $2750 as a minimum.

Rental car rates are pretty fluid and you can often pick up a discounted rate in "off" periods. Typically, weekends, as the primary market for rental cars here is business.

There's another possibility for reducing the rental rate: We have an "Entertainment Book" (costs A$60) which gives discounts on car rental, hotels, restaurants(fine, casual & cafe), theme parks & tourist attractions, museums, spas etc.
www.entertainmentbook.com.au

For example: Avis's specials are:
1. $20 off a weekend rental (min 2 weekend days)
2. Rent 7 days pay for 6.
3. Rent 30 consec. days, get $100 off.
4. Rent 2 weekend days & get next (consec) day free.
5. Rent 7 days & get one bonus day free + upgrade.

All the major car rental firms (Hertz, Budget, Europcar & Avis) are represented & all have various discounts.

You might also try Delta - they're usually quite inexpensive.

If you belong to an Airline or Hotel loyalty programme, you might find it will give you discounts with the International rental firms.

Alan's right - wait until you get here, unless someone makes you an offer you absolutely, positively can't pass up in the meantime.
Avis will let you cancel if you find a better deal.

Good luck, hope this helps & sorry for being a "tail ender". Thanks Alan, I missed seeing this post.

Thank you for all the useful tips. will definitely try and keep my options open. Thank you Bokhara for the warning abt the CDW.

I just checked my travel insurance (with Vero through Covermore). It covers $2,000 CDW and costs A$25 per $500 to increse to max $3k. So, for more than 2 days rental, it's a better bet than Hertz's $25/day. Other policies will no doubt vary.