There was a stop conveniently located next to our hotel so we booked direct with the agent at the stop. We got off three times and all the conductors were informative, enthusiastic and charming each in their own ways. This definitely added to the experience. If I recall Philip, Steve, Deb and Boxcar were the conductors.
Like anything, the earlier you set off the greater the time you can spend at the different locations. We particularly enjoyed Balboa Park, Coronado and Old Town. Having had a taster we may be tempted to come back for longer.