Sure! I am from California, for the record (LA area). I have had 12 interviews and think (perception may be different than reality LOL) they have all gone really well. My interviews at Kaiser, UCLA, UCSD (all of which I recently received an acceptance to) were good too, but didn't particularly "stand out" compared to the others. I haven't received any post-ii rejections yet, so holding out hope for the others. To answer your first question, I have always been a very extroverted person and have befriended people quickly my whole life! I think that quality was apparent throughout all my interviews and I always had my interviewers laughing at some point. Almost all of my interviews have ended with "we hope you choose us among your acceptances" or "let's grab coffee when you get in", but I am not sure if these are things they say to everyone? Anyways, just try to be as a laid back (but not too much) as possible and be your natural amazing self (always rolled my eyes when people say this, but it is TRUE). They are trying to gauge if you fit into their school; so, if you put on a facade, then maybe you won't actually fit in?...
Also, do remember that the interview is just one part of this complicated puzzle that many of us will never fully be able to grasp. I do wish there was more transparency on the admissions side, but there is just too many of us applying, I think. To answer your second question, I really do not have a top choice at the moment...will come down to a combination of $$$, location, and doors opened/opportunities. My interviews at UCSF, Harvard, and Yale went pretty well...so we shall see!