Well, I feel bad that I always seem to point to a reference on renntech.org but there is a 3rd radiator install instruction that show how to remove the front bumper on a 996 and I believe that it's similar to the 986.
http://www.renntech.org/forums/index.php?act=diy&code=diy_rad
I'd be a little nervous using a cleaner without removing the front bumper.