To dream that you are crying signifies a release of negative emotions that is more likely caused by some waking situation rather than the events of the dream itself.
Your dream is a way to regain some emotional balance and to safely let out your fears and frustrations.
To see someone else crying in your dream may be a projection of your own feelings onto someone else. If you do not cry in your waking life, then seeing someone else cry may be a little easier to deal with then seeing yourself cry.
To wake up crying represents some suppressed hurt or previous trauma that is coming up to the surface. You can no longer suppress these emotions. They need to be dealt with head on.