From what I've seen, regardless of what neighborhood you live in, and what plot you pick, you will probably eventually see the various Sims, from all available neighborhoods eventually pass by the sidewalks outside your door. However, what I have noticed, is some plots do have a lot more traffic. Corner lots seem to have a lot more traffic actually pass close to your front door. If you're a social Sim, you can go about your business in your backyard, on a corner lot, and have plenty of people pass by within chatting distance, during the course of a day, provided you're not at work.
That's just my experience.
