Hey Maramu,
The track in/out is usually graded pretty well and is fairly hard albeit corrugated. If you go early August, as I did a year or two back for surfing, there may be a bit of rain around which creates some pretty big puddles on the main track. I'd be a little wary going through big puddles in your Subi, I found a couple of them a bit deep which was OK in the Patrol, but in a soft roader may be a bit scary, especially if you hit em fast.
The tracks from Red Bluff to 3 Mile to Homestead and Gnaraloo Bay are easy and a 2WD will get through, but as someone said, you will need a more serious 4WD to get to Turtles.
We may even see you up there in August??? Have fun!

Good waves,