Yeah, I really don't understand using any of these sprays. Here in the Northwest it is extremely windy much of the year and I wouldn't trust it not affecting me as well. I'd rather give a woman a loud whistle for alerting nearby people.
That in combination with the word "rape" yelled will bring even the most ignorant self serving do nothings to the rescue. There are very few human beings whom will stand by idly without at least checking it out.