
Milo v3 |

You can not project to the material plane. nor can you project to the same plane you are on.
There is no actual mention or suggestion of either of these in the rules.
Even if not being able to project to the same plane you're on is RAI (you can do it by the rules though), there is no reason to infer that you cannot project to the material plane.

Slithery D |

At best the RAI could be you can't form an astral projection on the plane you are on and you can't form one on your native plane. But there's nothing special about the material plane. Several statted demon lords have Astral Projection as an ability, and I'm sure they can use it to visit the material plane.

Mechagamera |
I would say that your astral self can find its way onto the Material Plane, based on (http://www.d20pfsrd.com/magic/all-spells/a/astral-projection):
You project your astral self onto the Astral Plane, leaving your physical body behind on the Material Plane in a state of suspended animation. The spell projects an astral copy of you and all you wear or carry onto the Astral Plane. Since the Astral Plane touches upon other planes, you can travel astrally to any of these other planes as you will. To enter one, you leave the Astral Plane, forming a new physical body (and equipment) on the plane of existence you have chosen to enter.
However, as I interpret that paragraph, if you do have your astral self running around the Material Plane, it won't be as an invisible, intangible "ghost", but as basically an animated clone.