
Because a dog is off lead is no way meaning that they are a good dog, or the owner is responsible.
It pains me to say it but we were mobbed by 4 off lead staffords one day, our poor girl (also a SBT) didnt know what to do and they were litrally roaming free while their owner was somewhere else.
I would always approach with caution and I now assume every dog is a bad dog until proven otherwise, its sad but saved Mitz from a fair few run ins, as ones who have lookd friendly off lead a little way away have turned out to be snarly horrible dogs with no discipline or training, but then some have been lovely and very friendly.
Just be careful and dont assume they are nice till you are close enough to see body language etc :)