There's another review of SV, this time at Game Revolution. It describes the interactions between tourists and other people:

" The big losers in this expansion are Sims looking for a little rendezvous with their next door neighbor. This can quickly turn into the vacation nightmare. When Sims vacation alone or as a family, the player can control all members of the traveling party. But when one Sim asks a neighbor to come along, the game operates the same as it does when a Sim asks another to Date or Hang Out in the Downtown mode of Hot Date. The vacationing companion will arrive with a mood crystal above their head to let you know their most pressing need. You won't be able to actually do anything about that need, at least not directly, because you can't control the companion."

The final grade it gets is a C, with negative points being the limited interactions, an 'autonomy issue' and that the neighborhoods are still separated. I doubt the last thing will ever happen though... You can read the full review of Vacation over here.