well.. at least finally there is a product that does what it is intended too.. lol.. i'd suggest this stuff called "goo off" it is like a yellow bottle, with yellow liquid.. it worked to get the glue off my windshield on my other car.. give it a try
Start off with a hair dryer or a heat gun to melt the glue a little bit. Then take dental floss or fishing line, and gently slip it under a corner of the sticker. Again, GENTLY, wiggle the line under the sticker to peel it away from your bumper. Keep doing this, and take your time. After you get the sticker off, use some goo-off, or some 3M Adhesive remover. Be sure to wash your car well afterwards, and then wax it.