The Big Avocado Halved is along the Pacific Hwy shortly after crossing the border. I had originally logged it as a Big Avocado but there is another whole Big Avocado at the entrance of Tropical Fruit World.
The halved fruit is placed to alert traffic of the upcoming exit required to go to Tropical Fruit World with the sign directly underneath it. Tropical Fruit World is a brown sign itself so you will be able to find it here on Brown Signs.
Being on the side of the highway you will need to take care of where and how you pull over. There is a side road that basically leads to the side of the big thing. Regardless if you pull off on the side of the highway or on the side road, you need to be travelling south.
If you are heading north on the Pacific Highway, the safest option is to continue north and take the exit for Chinderah and Kingscliff with a brown sign for Tweed Coast. Use the roundabout and re-enter the highway heading south. The Big Avocado Halved is about 1.4km along the highway.