How long does it take to walk through the garden and see the lights

At least 2 hours

I would say you can walk it in 2 hrs, but if it is a perfect pleasure night it will take longer. You will stay and look longer at the displays. Because you may witness a wedding proposal in/at a display. They do 300 weddings a year.

The golf cart guided tour which is $15 a piece extra per golf cart takes 45 minutes!

I would allow at least 2 hours but you can easily spend 3 hours.

Couple of hours