If you are only staying in Sydney I would stick with public transport, busses, ferries and trains are all very good, easy to use and not expensive. Sydney does have some traffic problems.

Yes I agree with Judith lots of one way streets and it is a bit hard to get around if you do decide to hire a car there city pick ups and the hotel Menzies should be able to get a hire car for you it will most likly to with eoropcar they have them on there web site
If you want to do it your self Avis city pick up is
395 Pitt Street
Hertz is William street on the corner of Riley street

Europcar is 100 William street

Budget is 75 William street

To get maps of the city go to
http://www.whereis.com

It will give you maps if you type the adress you will be staying in The Menzies in Carrington street it will cost you $29.00 to park your car at the hotel at night hope this helps you and you have a good stay in Australia

In Sydney at present on holiday, the driving here takes a bit getting used to to say the least! Before hiring a car, a good book of maps is essential. We hired from http://www.bayswatercarrental.co.au Their premises are also on William St. They are a big company, good cars, and are cheaper than the likes of Avis and seem to be used by lots of people staying in that area who dont want to spend too much and I can thoroughly recommend them. But be warned Sydney driving is not for the faint hearted as its a confusing place to drve in. Alan

If it's main places of interest you want to visit there's no need to drive. There is a monorail/tram like service which takes you right to the doorstep of most of the main tourist attractions and it's pretty inexpensive to get an all day pass.

Having re-read a coule of old posts, just to let you know that Avis rentals at the airport do have Sat Nav in all cars. The staff will also show you how to use them, if you're a technophobe like me.