We generally enjoy the hop on hop off trolly tours. It's great to see the city and learn some history.
However, the St Augustine tour was disappointing. The city is small, geographically speaking, and certainly walkable (we are both good to walk, but not forever and ever). I think the tour is less than great because the town space is so small - you really drive by the same things over and over, and there isn't much time between stops to hear much about the city.
The drivers were good.
I would pass on this one, put on some shoes, and enjoy the sites instead of spending the money. Too much $ for a short ride around town.