i guess all the videos with sound are made with go pros. But I would like to know if there is a way I can do it with My phantom 2 vision plus

There is no microphone on the camera.
Of course you can attach some sort of recording device and edit that in later. With some training it shuld not be to hard to get the audio synced.

Use some kind of visual cue that also makes a sound on both ends of the video then make sure the visual cue and the sound matches up on both places.

You can get a small digital recorder that you can velcro to the bird.  As said above, just give yourself a cue on the vid for synch purposes.

mmm strange i just made a post here and its gone, ..

To answer the question, fitting a microphone to your quad will result in videos full of the buzzing of the props, go watch youtube where someone has recorded using a Gopro camera to hear the results, best bet is to add music and voice over post edit. if not people will reach for the volume control when your video comes on.

Might be why DJI never bothered to fit them.

Have a look at http://youtu.be/z8G7IPL7CHU and see if it's what your trying to do?