Supposedly I have them..yet...I don't see anything in the manual or in the vehicle that says how to turn them on. Any ideas?

If I remember correctly from reading the manual, they come on automatically when the rear defroster is used. I would have no personal experience with them in Tucson!

You might try looking at ToyotaIGuide.com

On my Maxima, it seemed like they were always on regardless of the rear defog switch. After a period of time there may be timer/relay circuit but I never bothered to look. When there is dew in the morning, check the mirrors and watch to see if they clear off before you start driving.

I agree. It has been brought up a few times.

Absolutely. The rear window defroster button controls the rear window defroster AND side view mirror heat.

Like they say above, just turn on the rear defroster. If you are unsure if they are working, turn on the defroster for a minute or two, and then roll down your window and feel the surface of the mirror- it should be warm.