my hubby has signed us up for a cruise that leaves from sydney and ends up in los angeles. we want to fly to australia a couple of weeks ahead of the cruise departure and do some sight seeing on our own. we would like to make our way to the great barrier reef and back. are there trains, buses, can we rent a car, or do we need to fly? hubby read somewhere about some kind of plane hopper ticket. can anyone enlighten us on that? i thought a train would be fun..if there is one.

G'da ther Laim's nanna!
If flying into Sydney, you have many options when travelling up the East Coast. It is quite a distance though, probably about 1800miles (3000Km) to Cairns.
Coach (touring bus) or train from Sydney to Brisbane then 'The Sunlander' (train) to Cairns. Coach is also a possibility & of course you can drive, but I would only do that one way.

Why not consider flying into Cairns, it is tropical, geared up for the tourist and you can access the Barrier Reef. Why not then Drive South via Townsville (visit Magnetic Island) then on to 'The Whitsundays Islands' (Check a map for Proserpine & Airlie Beach) this is a popular access point for the GBR.

At Airlie, there are lots of GBR related tours and island trips. Maybe then drive on to Mackay and take the train to Brisbane and go on to Sydney via the Gold Coast and continue South along the coast road (by Coach). . You can do all this comfortably in a couple of weeks, could probably squeeze in a ferw days in Sydney too.
I personally don't know about a 'plane hopper' ticket although this type of thing is available with coach lines.
Weather may be a consideration it could be rainy in Northern Queensland up until about April.
BTW, I'm from Melbourne but that is the other direction so come here another time.
Enjoy your time in OZ & your cruise the LA.- sounds fantastic.
Cheers - Barney

Depending on your time of travel. In Queensland, December to March will still be hot but with regular rain and storms in the North, Tropical Cyclones (Hurricanes) are a real possibility. So this is not the best time to visit Queensland, especially if you are here for only a short time. Any other time go for it.
Northern Australia has 2 seasons the Wet & the Dry. The wet (in broad terms) is November to April. With the peak of wet weather being January to March. The temperature though will still be warm to hot. The dry is the other 6 months with very little rain and lots of sunshine.
January to April is the optimum time to visit Sydney & the Southern states.
Cheers

It has been wet with some flooding in Northern Queensland. As I write this, a tropical Cyclone is building along the Coast so it may get a bit wet & wild up there