There's a reason 'Banquets' is the first button after 'Home' on their website.
My husband and I were very disappointed that our last night in San Francisco in October 2006 was spent at Fior d'Italia feeling like the family black sheep at a distant cousin's wedding. When we arrived for our reservation, there was a bus (not a short bus from your school days, but the holds-70- people, full-fledged Grayhound/Trailways- type bus)unloading a huge wedding party. A separate and also very large wedding party had already been seated in the main part of the dining room.
We were seated in a small back room, the kind with movable walls like banquet halls use. It was impossible to have a conversation over the roar of a room full of wedding rehersal dinner revelers on the other side of the wall, not to mention their cheesy wedding music. While the waiter was professsional, pleasant and sympathetic to our situation, there really wasn't much he could do about it.
There was nearly an hour between the time we finished our first course and the arrival of entrees, presumably because they also had roughly 150 people other people to serve at two banquets. While I enjoyed my osso bucco and bagna cauda, I suggest you make reservations only on a weekday and only after inquiring about any banquets coinciding with your reservation. You could try asking to be seated in the bar which seemed pleasant enough. On second thought, I would recommend you let this 'restaurant' concentrate on the banquet business it so obviously values over its service to couples and smaller parties. There is just no way for a small party looking for a pleasant evening out to compete with a party of consisting of dozens of people. I know San Francisco offers better experiences.