While I am sure that there is a use as an aide, and I have known blind people who are both patient and very independent, I doubt they would stand on street corner waving a phone around hoping to catch some text.
That doesn't rule out that text to speech with translation wouldn't be beneficial - just not in this context imho.
Blind people are patient by necessity, I'm sure there are many who wouldn't mind waving around their phone scanning for text.