@PirateJandcats: Hi! If you mean when you open the front door and enter right into the living room, then yes, most houses on the West coast of US would be built "open" like that. It gives a sense of spacious and airy environment, especially desirable in a smaller home like the Newbie's. Most all the houses I re-do in the Sims, I always tear down walls and open up the place to bring in light and make best use of space.
Another advantage: Sims can move around more fluently in an open layout, and you can see them easier during play. There is also a game-tip pop up to that effect in Sims 1: It states that Sims like large rooms with lots of corners and windows to let in light. I don't know if the same is true for Sims2 or Sims3, though, but I've always kept that in mind.
We do have hallways where I live, but they usually lead toward bedrooms. Try doing an online search of contemporary floor plans in Southern California to get more ideas on what homes look like here. :)
