When you enter the sally port into the Star Fort, you will see where there are trees with a red painted band. These are property lines, and also on the left side of the palliside wall you will also see a concrete boundary marker. Actually, from the Star Fort, you can see where Rowett's Redoubt was located, there is now a house built on what was the redoubt.
When you walk the trail, you have nothing to worry about straying into private property. From the parking lot, as you start to walk down into the Pass, you will notice on your left the red banded trees. Just stay to the right, and you will be ok.
There is another Federal fort located on the ridge on the right hand side of the pass, as well as Federal trenches. All of this is public land.
I forgot to mention that you may want to wear comfortable hiking shoes as the trail can get pretty steep, especially from the inside of the pass to the Star Fort. Allatoona Lake also joins the battlefield on the right side of the pass, so if you like to fish, you may want to bring your fishing tackle.