What sort of fish are you after? I've got family on the gold coast so have fished there heaps and there are plenty of fish. The biggest problem in holiday periods tends to be the number of other fisho's and boats on the water.
Off the beaches there are plenty of good light gear fish... whiting, dart, etc that will keep you amused for hours.
Despite all the 'shark' talk about the canals and rivers, they're not really any more prevalent than in places like the harbour... you just tend to get them in unusual places and they're pretty aggressive in the murky water. Personally, I wouldn't swim in the rivers or canals (in deep water anyway) anywhere north of about Coffs Harbour.
A couple of summers ago an old guy got taken on the Gold Coast than only the summer before had been interviewed on TV after another attack giving the predictable "I've been swimming here for xx years an never had a problem" quote. If you had a way of predicting the wrong place, wrong time "equation" it would be ok, but since you can't you're taking a risk.
I've caught a couple of sharks in the canals.... always at night.... but that's the only time I've fished for them.
If you get access to a boat, try to get your hands on live herring or small pike and drift channels, rock walls, jetties, deep holes. Everything eats herring up there.... big bream along breakwalls, big lizards, Jewies.
The one thing I've really noticed in Southern Queensland is that the saying 'no run, no fun' seems more true than anywhere else I've fished. At slack tide things seem to go really quiet everywhere.... rivers, beaches, reefs. The more water movement the better as long as you fish the right spots.
Hope this helps... I'm sure there are residents that have much more expertise up there.
Cheers, Slinky