Op, if you didn't see the dog do the poo then it would be very rude of you to ask her to pick it up.
Although dogs are trained to poo on demand, they do have off days, such a funny tummy. It's not always possible to notice that they have done a poo either, some dogs are quite sneaky about it and will poo whilst they're walking.
If my husbands dog does a poo, then he will clear it up. (no sight, a case of fumbling round the pavement.) if someone offers to pick it up that is obviously greatly appreciated, but certainly not expected.
If someone asks him to clear up a poo that doesn't belong to his dog, then, well insert any rude response you like back in this space 
Ps, I don't know about other dog owners, but Dh and other friends who are registered blind do generally carry a supply of dog poo bags.
To the person who wanted to know about speech reading software, jaws for windows is the best, although very expensive.