From Metro to Barcelona Cruise Terminal B

I'll be making the same trip in October (Virgin Voyages). I think that the link below might get you the information you're looking for. Not sure if the metro will take you all the way to the World Trade Center, but it looks like you'll catch the cruise terminal shuttle to your ship from there.

I hope this helps!

https://www.barcelona-tourist-guide.com/en/transport/barcelona-cruise-port.html

Miss the ship and spend a week in Barcelona.

From the Drassanes Metro station, it's a 15 minute walk down the Las Ramblas to the World Trade Center, where you catch the cruise bus. The bus coordinates it's schedule with cruise arrivals and departures.
It's a long walk (2 kilometers) from the World Trade Center to Terminal B with little or no pedestrian walkway.
In the event that the cruise bus isn't running I'd take a taxi from my hotel to Terminal B,
What makes you believe the Cruise bus only goes one way? The blue bus has a circular repeating route from the World Trade Center, to the Terminals including Terminal B.
https://www.barcelona-tourist-guide.com/en/faq/cruise-ship-terminals/shuttle-bus-barcelona-cruise-terminal.html

Take a taxi and relax

We took a taxi. It was very reasonably priced.

Taxi. It's not worth the hassle.

Thanks so much for all your input! It was very helpful and fun to read. Now for the next question about transportation in Rome...on a different forum.