Question for anybody that has done Malta excursions on Mariner (or Voyager).

I am interested in seeing St John cathedral in Malta. My understanding is that this cathedral is in Valletta. Indeed , there is a Valletta excursion that takes you to that Cathedral. But in reading the description of a couple of other excursions that go to Mdina, they also say that once there they will take you to see St John Cathedral. I believe the Cathedral in Mdina is called St Paul. Is this an error on Regent excursions's description? Anybody has been to Malta recently and taken an excursion through Regent? If so, which excursion and did it take you to St John Cathedral?

In case we want to do our own thing, is it easy to find a taxi at the port. Or is it walking distance from the port to the city?