Australia??

I live in Sydney. Depends what you want to see. Sydney is good, but I have heard Melbourne has better nightlife. I have been to Cairns and I really loved it. Port Douglas, which is by Cairns, is a great honeymoon spot. Also the Blue Mountains is a great place and romantic for 2 nights.

You need to give yourself at least 2 weeks.

If you had two weeks I would do this:
Land in Sydney, Explore for 4-5 days.
Go up to the Blue Mountains and stay for 2-3 days. @ nights would be good, 3 would be better.
Go up North to Cairns/Port Douglas and do a 6-7 days there if you do both. Cairns is a small city, so not much to do and the beach is mud. But a good place if you want to do snorkelling/diving excusions. Port Douglas is good, b/c the reefs there aren't so touristy and the coral is in better shape.

I don't know what you really like but a few more suggestions:
Hunter Valley (5 hours from Sydney) for wine.
Margaret River Region by Perth
Whitsundays Cruise.
(can you tell I like wine and snorkelling?)

Please remember Australia is as big as the US and a great big desert in the middle. You have to fly to cities.

ATM we are having a bad rain spell b/c of La Nina. There has been a lot of flooding up in Queensland. The weather people expect it to be rainy until May. By the middle of May it gets cooler. As I sit here writing it is 70 degrees, which is quite cool for here b/c it is the end of the summer.

That is all I can think of. Let me know if you have any questions.