After reading the reviews on both of the main hop on hop off tours in Savannah, many of which complained of not being able to hop back on due to long lines, i decided not to prepay online for a ticket. Instead I went the main Savannah visitor center (where all the tours start) first thing in the morning and saw that first. The lady staffing the visitor center desk told me that the historic district was just 1 mile across and that you could easily walk to wherever you wanted to spend more time after taking a tour. So instead of a hop on hop off ticket, I just got the 90 minute tour ticket from Old Savannah Tours, which saved $7. The tour was fine, you get on the same trolley bus as the hop on hop off people, you just don't get a wrist band to get back on, so stay on until you get back to the visitor center. It was a good orientation tour, and afterwards was easy to walk to the places I wanted to see in more detail. Also, there's a free Dot Shuttle that runs through the center of the historic district that stops at 18 sites, so you could just use that for hop on hop off. Parking at the visitor center was inexpensive, I spent only $4.50 to park for 5 1/2 hours (you do have to pick your duration when getting your parking ticket).