On this itinerary we sailed the new Costa Fortuna that started in Rome and included Barcelona, Palma de Majorca, Tunis, Savona (Portofino), Malta and Palermo.
I've read some reviews and it's mentioned that Costa mix international guests on their tours. We did not find this at all. In every tour we took we always had English speaking guides. When you disembark the ship you are directed to a motorcoach that will display a sign "ENGLISH". I noticed all the other nationalities had their buses as well. The French had "Francais" on theirs, "Espanol" for the Spanish and so forth. The only tour that had mixed nationalities was a bicycle tour in Palma and that was more of a bike ride than "tour". I highly recommend these bike tours. If you can ride a bike you'll love these tours. We took the one in Barcelona as well and we loved them both.
The one port on this itinerary that is a MUST for an excursion is Tunis. The port is in an industrial area and is not walkable nor safe. We elected to take the excursion that included Carthage and a local museum. The guide offered to include a bazaar although it wasn't in the itinerary. Everyone said "sure!" We later learned this was so he could take every one to his buddy who sat us all in a big room and showed us carpet after carpet after carpet.... I eventually decided to leave and take in a little shopping - half the room took my cue an followed! The tour finished up in a delightful seaside village with time to shop there.