Dusty, I would sugest you get used to it because its a great way to know how many pollys you are working with. some game engins dont suport double face so you have to create the faces on the other side. by now seeing them in max, is a way to remember that you have to create them if you wanna see them.
BUT if you really dont want to bother, you can allways go to object properties and uncheck backface culling.
ndchristie: "which is also the point of a symmetry modifier "
well yes but hear me out. if you are workign on a mirrored instance you wanna be doing that from the first moment. not modeling something and in the end applying a symetry and seeing the result for the first time. which makes you then apply the symetry at the beginning, then going down in the stack and checkin the "show end result" button to get to see what's happening on both sides. what happens with that is that you will allways get those annoying yellow lines.
so the best would be: modeling using a mirrored instance. when finished, delete the instance, apply the symetry and check for any mess along the middle edges.