It's funny just the other day my wife was saying on her next car she wanted front sensors so they would pick up those concrete barriers (like the monster ones at our local Post Office). Her current car only has rear sensors. I told her that the front sensors wouldn't pick them up anyway.
I can't imagine how you could angle the existing sensors lower without it looking funny/bad. However, what about installing a second set, or replacement set, of sensors mounted under the license plate area?