It depends on the photo. If the person is standing alone, with nothing in front or behind of him or her that you want to keep, the recompose tool may work. Otherwise (removing one person from the middle of the back row, for example) cloning may be your best bet.
Use Spot healing brush tool t oremove such objects. Here is the help link to do this http://helpx.adobe.com/photoshop-elements/using/retouching-correcting.html#remove_spots_an d_unwanted_objects. If you face any issue do let us know