My Dad always carried a big walking stick when out and about in the neighborhood. OF course, you would have to be willing to whack the aggressive dog with it to be effective. (I don't think I could)
Wouldn't regular Mace work on dogs? (i.e. pepper spray?) Sorry to hear you have such a negligient owner on your walk. hope she learned her lesson and will buy a proper tie-out for that dog.
luckily, the people who used to live next door with a very aggressive dog moved. I wouldn't let DD play in the yard when it was out. I'd never walk my dogs up "their" part of the street. it was extremely frustrating.
did I say one project at a time?