I live near a large park along a river that is deemed an off leash area for dogs. My dog stays on her lead when we walk for a number of reasons.
When we are walking along and I see an offlead dog ahead I stop and wait. Some people notice my dog is on a lead and we have stopped, they call their dog back and either put it on a lead or keep it next to them as we pass. Others pay it no mind and let their dog carry on coming towards me at which point I ask them to call back their dog. Sometimes they do and their dog listens, sometimes their dog doesn't listen and they have to come and get it away. Those that do nothing at that point get some choice words from me; as well as advice that if anything should happen to their dog it is their own fault. If anything happens to my dog I believe that is also their fault and I will respond accordingly.