I don't have any pyrs, and consider Jackie to be far more the expert on pyr-personality than I will ever be. I can only say that I was really apprehensive about letting Merlin and Strider off leash at the dog beach Memorial Day week end with Julie and Aaron. We brought 30' leashes for them, but when it became clear that they were going to behave with 100+ other dogs running around we tried it out without the leashes. Not only did they behave, they stayed within about 20' of me on their own, and if I was not in their sight, they would panic, and race to find me.
Raven, on the other hand could not be trusted and stayed on her leash. It depends on the dog, and as long as you are prepared to fetch her back and deal with whatever happens....You'll never know until you try.
Stella