That really depends on where you're staying, but I'll assume you can travel anywhere along the coast.
Brisbane is nothing special, it's a standard city. Surfer's Paradise has become too commercialised and it's both expensive and boring. The Gold Coast is still okay, and it has a few theme parks that are all fun but nothing compared to theme parks in the Northern Hemisphere.
Head further north than the south east and you'll find beautiful places that provide services to tourists, but without the concrete jungles and expensive shops. Mackay, Maryburough, and further north Cairns, just to name a few. I strongly suggest you head north of SEQ, because then you can see the rainforests and they are magnificent.
To sum up, Queensland is worth seeing for it's natural beauty, not it's cities and towns. Stay on the coast, but north of Brisbane, SEQ and basically north of the sub-tropical areas. Stick to the tropical places.
Just remember; south east Queensland (SEQ) is where the residents of Queensland live their boring lives and do day-to-day things, and the coast north of Brisbane is where tourists go to appreciate some of Australia's natural beauty.
Sorry to disagree with the person above, but DO NOT go to Townsville. If you're catching the ferry to Magnetic Island, sure, but don't stay in town. It's population is mostly aboriginal, and they're not as friendly in real life as they appear in advertisments, believe me. They'll abuse you when you walk down the street. I wasn't physically attacked because I'm a guy and they're cowards, but if you and your friends are girls they might.