My dog is about 5 months old, medium sized mixed breed, very friendly and playful and loves people and other dogs alike. She has started going off-lead a little bit on the beach or in the park when there's no one else around. Her recall is ok - brilliant if there are no distractions but not if she'd rather be chasing a bird, rolling around with something smelly she's found, etc.
Today I took her to the park and there was a group of dogs all playing together, I asked if she could join in and was told yes of course. So she did and had an amazing time! She was running around chasing and getting chased by the other dogs, running up to everyone for pats and cuddles, getting knocked over and yelping but getting back up to play some more. It seemed like she was having loads of fun. She did come back when I called her for a treat.
So I'd like to feel comfortable letting her off more often. My question is - how do you decide when to let your dog off to play and when do you think "oh no, better not". Obviously if there are small children or elderly people about then no. But what about when there are other people walking well-behaved calm dogs around when I knew she's just going to run up to them wanting to play? Basically what are the unwritten rules?