if they are perpindicular to the beam ( you are shining it at them ) yes they will see it, even several miles away.
If you shine it straight up, beyond a few hundred feet they won't see anyhting unless you hit a cloud or something, and even then they'd probably miss it unless you could tell them exactly wehat to look for.
The laser light is coherent, when it reflects it scatters everywhere. So unless you are along the path of the beam before the light gets scattered it will not appear very bright.