Is it safe to use mothers chrome polish on the upper grille?
i want it to shine like the bumper does.

Yup.
You can't beat your mothers.
Then take the rag you used to do the chrome and polish the glass. You don't need to add any more Mothers to it but it should knock all the water spots off.

I've used Mother's Chrome Polish on the upper grille. Works great!

cool, thanks. i'll get that cleaned up today.