If your worried dog is happy with other dogs, which many are, then meeting other dogs on walks will be fun. It's important to stay aware though because unfortunately some loose dogs can cause trouble. Just as you are learning to read the body language of your friend, I suggest you take some time to understand the intentions of others.
The world we live in is awash with dysfunctional dogs, which is sad but true. With little opportunity to learn from well-balanced elders who teach manners to their young friends and family, dogs can become thick-skinned thugs. It’s not their fault but their behaviours may include running up and getting in another dog’s face repeatedly, jumping in or knocking a dog over, not reading a gentler dog’s behaviour, and ignoring natural cut-off signals. All of this can be overwhelming even for the most social dog. Don’t get me wrong there are a lot of wonderfully empathetic, kind, and genuinely responsible dog walkers in the world and they are truly a pleasure to meet. It only takes one that isn’t, though, to affect the wellbeing of our dogs forever.
Sadly, sometimes people have their dogs off the lead and don’t recall them, even when the dog is aggressive towards others. Unfortunately, we can’t completely trust people to be thoughtful or sensitive to the needs of our dogs, so we have to be prepared to protect them from stressful experiences on our own. Often these people can’t read the intention of the dogs they are with and so simply don’t know what their dog’s body language means.
If you find yourself shouting at someone not to touch anyone or anything who doesn’t belong to them, live and learn. Don’t blame yourself, we are only human after all. Sometimes being ignored by one more fly by petter is one too many and they become the straw that broke the camel’s back, especially when you’re in charge of the welfare of a dog who is overwhelmed or worried.