Vistied while in town for a ballgame. Church is located 3/4 mile north of Camden Yard. We took the light rail with a stop a couple of blocks away. Also served by the Charm City circulator. We attended mass with our three kids 8, 11, and 13. While we did not have time to take a guided tour the church was beautiful inside and out. Kids enjoyed seeing the church and parish members and clergy were friendly. Kids plan to proudly tell their classmates they have visited the "oldest cathedral in America".
Note that the Cathedral is not in a primary tourist area like the Inner Harbor so there are some homeless located in the surrounding blocks but nobody bothered us. Well worth a trip if you have the time.