We've visited St. Augustine several times and have always walked. This was the first time taking the Trolley and the only reason for doing so was we had discounted tickets.
For transportation, it's a great way to travel from the historic downtown area to the Old Jail Museum area as the walk is about 5 miles one way.
For exploring, you can hop on and off at 22 stops along the way.
For historic information, it will depend on your driver. We had 2 drivers who, along with historic information, included some corny jokes was a bit annoying. We had one driver who gave so much information, we wanted to ride around the city a second time, just to hear more.