Whenever I travel the Hop-on Hop-off is always on the list. I find they are a great way to get ones bearings, and also provide inspiration for place to visit.
Compared to those of other cities I didn't find it that informative, unless Scotty was your driver. Scotty was fabulous, he provided useful meaningful information. Talked knowledgeably about San Diego, with some humour. The other 2 drivers were dull, one was particularly so. They communicated little about SD, more about the plants.