Why not call RCI Shore Excursion dept on 01932 834325 and ask? From Villefranche to Monaco it is very quick and easy to take the train or the bus.
The bus station is straight up the hill,in the main street,
to the train station ,turn right from the jetty,along the promenade to the end,u can see it clearly from the ship,look for the overhead cable,easy 5/10 min walk,on the level,steps up to the platform,ticket office on the side for Monte Carlo.
The bus is #100 and it costs €1.30 and takes 1/2 h.
I've done this with another cruise line. There is a huge underground/multi storey car/coach park just 100 yards or so from the back of vatican. If you follow the wall around to the front it takes you right into the main square of the Vatican/St Peters Square. The hop on hop off buses also depart from just outside the Square. It was 13 euros each last year. If tyou are going on a Sunday when or just after a service has been on, the buses tend to skip this stop because of the number of pedestrians walking down the road. We wnet to a service and just left a 15 minutes before the end and instead of only waiting a maximum of 15 minutes for a bus, ended up waiting for just over an hour and a half. There are 2 different companies that do this type of bus tour and neither sell the tickets on the bus - but you can buy them for a newspaper/tobacconist kiosk opposite the bus stop. Hope this is of some help to you.
If you have already booked your Rome alone excursion then fine. If you haven't then may I suggest you do what so many do and get the train into Rome. This is so much cheaper than the tour and much faster. The trains go to Rome Terminus and from there you can walk around most of the sites in a day. Neil Dow.
We visited Rome with RCI this May and did the Rome on your own trip. The bus drops you at the underground bus park but the guide takes you to the front of St Peters Square where it is an easy walk to the Trevi Fountain, etc via many of the wonderful sites Rome has to offer. Beware - stay away from the horse and carraige rides unless you take a HUGE wallet with you. They are VERY expensive.