Beware of "Reserved for Private Party" signs. While it's common practice for many restaurants to cater private parties on the premises (despite the extra work), it sometimes doesn't make a lot of fiscal sense to close down the entire restaurant for a few big tables. That's fine for the restaurant, but not so much for everyone else.
Since everything the private party orders has to arrive at the same time, the kitchen has to slog through dozens of soups, dozens of salads, and then repeat for entrees and dessert. This means that everyone else's food is going to be getting made late and begrudgingly by the overworked kitchen staff.