Having been an instructor and used that area extensively for exercises, having people walk/run/ride though the middle of your harbour area or patrol lane when you’re trying to install at least a bit of realism into the guys is a pain in the arse. This is especially true when you’re using blank rounds and pyrotechnics as the danger range for use with civvies around is over 100metres – basically, if we can see you, it has an effect on training. Unfortunately, I’ve been on the receiving end of some very inconsiderate people who can’t understand this and this is where the problem lies.
On the flip side, I had absolutely no issue with others using the area as long as they kept out of the way. Having worked with dozens of other instructors, I’ve not knowingly met anyone who thinks differently. As several posts above say, abide by the code of conduct of you come across guys training, ask where they are not training so you can go there instead. That way, everyone’s happy! 🙂