A four sided polygon has 2 faces (or tris) so roughly double your poly count will give you the number of faces, which is the number you want to keep track of for game models. A lot of people throw around poly count stats when its really the number of faces/triangles you want to keep an eye on.
Do this: make sure your model is an editable mesh, then press 7 on your keyboard. This will give you the number of faces in the upper left corner of the viewport. Doing this in editable poly mode won't give you an accurate face-count, however.
BUT: You can download a niftly little script from Scriptspot.com from a guy named Martinez that will give you an accurate face count no matter what mode you are in. Pretty handy for me since I like to work exclusibvely in editable poly mode.