I'm going to share a secret with you. Most of us would have at some point or the other, encountered a small dog on a leash that growls ferociously at us as we walk by. It will strain the chain, and make as if it was wishing it were free. My personal experience shows that this is just a display of bravado! In most cases, if the dog is suddenly left off the leash, it will simmer down and pretend you're not there. This is specially true with small dogs. They seem to have a bit of a a complex, and feel that they have to prove that they're just as good as other dogs!
Small dog on leash
Hence they will bark and strain and bare their teeth with you when they are safely at the end of a leash. But watch them when they're free. There will be nary a whimper out of them! Of course, this is assuming you don't take flight at the sight of one. Nothing pushes a dog's buttons more than a fleeing prey. It needs a bit of care to stay around strange dogs, irrespective of whether they're on a leash or not.