If you're looking straight down you are not going to get a whole lot of polarized light. One source of polarized light will be the sky. If you're looking down you won't see sky. Another source is non-metallic reflective surfaces, such as car bodies, etc. and partially reflective surfaces such as water or windows. Since water will always be horizontal, looking down at it will be perpendicular, so no polarization. Windows and reflective surfaces will entirely depend on the angles involved, so there's no real answer except "it depends." How well do you understand how light is polarized and in which direction?