You sound just like us...we love to walk, too, and find it a wonderful way to sightsee.
When we planned our visit to Saint John last year, I found the a wonderful Web site (click HERE
) with detailed walking tours. There are several, along with a map. I printed everything and took it with us, and we had a super day. We had lunch in one of the restaurants in the Market Square building. All but one tour is within a reasonable walking distance of the pier.