Good question; enough detail to give a decent answer.
Generally with good weather and a favorable breeze (one that’s close to abeam of the boat, meaning coming from the side, generally) the boat will make the best speed over the ground. A 52-foot sailboat should expect to move at roughly 6–8 knots in fair weather without working too hard. (It’s possible to go faster, of course, but that means crowding on more sail and then being very attuned to potential increases in wind speed that require more frequent sail changes.) Depending on the course to be steered, it may not always be possible to have that wind abeam. And I don’t know what the prevailing winds are in this area.
In coastal sailing one always has to be aware of tides and navigational issues such as fog (even on good days, fog occurs often in the morning and evening when the sea and land temperature differentials create it), and other boat traffic, particularly commercial vessels.
So I would suggest that you check a map or chart for the actual distances to be sailed, check a tide table for San Remo for the days you want to schedule this travel (because the sailor will know that he wants to leave port on the ebb – no sense fighting an incoming tide as you’re trying to leave port) and see if he can arrive at his destination during or at the end of the flood tide. Keep in mind that peak tides occur roughly 6 hours apart, but if you leave at the start of the ebb tide and arrive near the end of the next flood, you could have nearly 12 hours of travel.