Dont leave anything unlocked or sitting out in St George.
We were warned when we arrived at the caravan park by the managers, and sure enough theives were around that night and got a bit of stuff, not ours thank goodness, but they got into cars ect and got quite a bit of money and a very expensive camera somebody left in their car. They have also had them inside cabins at night while people slept.
Make sure you lock up. Apart from that we liked it there.
We now have a 500 watt sensor light that we plug in outside our van. Anybody snooping in the night gets a big fright when it lights up the park.
If you are looking to camp at the St George showgrounds I'm sure you won't have to book in advance. I was through there a few weeks ago, used the dump point which is at the back of the showgrounds.
I went into the showground looking for the dump point. A very nice caretaker came out and gave me directions. There was heaps of camping spots in the showgrounds itself. I'm sure you could just turn up.