The A La Carte Restaurant was for 1st Class use. 2nd and 3rd class had their own restaurants/dining areas. To my knowledge, the 3 economic classes didn't mingle amongst one another at all during the trip. Especially 3rd class. They were carefully sectioned off from the 1st and 2nd class areas of the ship...as this became a big problem after the collision with the iceberg. 3rd class had never ventured past their barriers and had Hell finding their way through the 2nd and 1st Class areas (which both had the only means to get up to the boat deck). Hope this helps a bit and if I'm wrong on any of this, someone please correct me. I don't want to steer Kristjan wrong.
>>I'm wrong on any of this, someone please correct me. <<
I don't think you missed much of anything. Class barriers were pretty strong then, and the strict segregation of 3rd Class/Steerage from the rest of the ship was a matter of law. Even if they hadn't been, I doubt that anyone in 3rd class could have even afforded the prices in the A La Carte Restaurant.