Please use a leash on your dog!!!!! Or take your large dog who needs to be run around to a dog park. The following has happened, oh, a billion too many times:
My little dog is on his leash either being walked by his responsible dog owner (who also cleans up his poop--novel idea) or lounging quietly on the patio. Off-leash dog (large or small, take your pick) comes *tearing* up to my little dog and begins to fight with him. Insanity occurs, with lots of barking and yelping and snarling and sounds that I never hear come out of my animal. My heart races as I scramble to pick him up out of harm's way, placing myself in possible danger as well. Irresponsible owner of off-leash dog comes running up, yelling at his/her dog with a terse "sorry" in my direction. Grabs his/her dog roughly for not following instructions and walks away.
One of these days, either my dog or I or both will be hurt by one of these dogs and it will be the sole responsibility of this irresponsible dog owner who is so casual about dog ownership that he/she just assumes "Oh my dog listens to me." Well, no, your dog doesn't listen to you. Not when there's a tasty smaller dog within reach.
Solve the problem! Walk your dog on a leash. Then you're not embarrassed when your dog "disobeys", your dog isn't strangled when you grab him and peel him off of my dog, and my dog gets to live another day. See, everybody wins. AND, it's a law in the neighborhood, so you're even being a good citizen. What a nice thing.