It depends on the causes that lead to people's blindness. In some cases, people are born to be blind and their eyes may appear as normal as others except that these blind people can not see. Then they can blink and close their just as normal people do. On the other hand, if people get blind because of trauma, hurt, cut and so on, and their eyes are broken and can not open as normal people do, then their eyes will not be able to blink. The optical muscles and nerves of their eyes are completely damaged and thus are not able to control the eyelids.
Yea, blind as they are, they can blink their eyes. Because it is the muscles of the eyelid that makes us blink. Blindness does not mean his eyelid muscles are also damaged, so the blind man can also blink his eyes as an automatic reaction to keep the surface of the eye moist.
If they still have their eyes, yes, they do blink. Just because they can't see, the eyes will still have feeling and need to be moistened, which is pretty much the reason we blink. .Well, that, and to remove dust and other debris off the eye.