In my county (rural) all dogs are "supposed" to be on a tie out of some sort or penned/fenced. We've got a neighbor 2-300 yrds away through the woods that frequently lets their Yorkie run loose. As far as Im concerned if their dog comes onto my property and close enough to our dogs 20ft lead right in front of the garage so that my dog harms it, then thats on them. So far the closest encounter was a couple of feet. Seems that the little Yorkie knows where to stop, to a certain extent. He still pees and craps on our property but hell, its the country. I aint worried about that.
In a suburban/neighborhood enviroment I wouldnt worry if youre dog is tied up on your property and other dogs are loose, thats on their owners. I would be hesitant to walk your dog though, leash circumstances can be tricky as far as legally whos at fault.