I finished my interview with USC so maybe I can help give some pointers.
1. Currently, all positions are fully funded and students can freely choose to go to either Caltech or USC for their PhD (Previously fixed at 2 Caltech, 4 USC - but students have informed that this was on paper only, there was still flexibility once you get in).
2. There is on campus housing 2 min away (walk) from the lecture halls. However, most students live off campus about 45 min away drive. Cheapest housing I heard about is around $500/mo in a decent condo. Student opinions seem to be that a car is a must because everything is very far apart. I've heard one student who bought a '92 used car using only stipend, but usually some parental help may be needed.
3. Many students rave about the school's board scores. What I heard is that their scores have been rising since they switched to the new curriculum a few years back. Apparently this year, they are only a couple points below Harvard.
4. I am not sure about this one, my impression is maybe 3-4 a year.
7. Definitely not, I have met students who have never had to use Spanish even in their weekly clinical course (they do patient interviews) in LAC. An upside is that if you do want to learn Spanish, they offer a free medical Spanish course and you'll get plenty of chance to practice.
Everyone I met during my interviews was extremely friendly so I don't think you need to be worried about asking questions as long as you are asking out of genuine interest in the school. You also get many chances to ask questions to student guides, who don't submit reports on you and have no bearing on admission decisions. Many students told us that they won't be offended by frank questions because they are there to help us decide. In fact, some of them also gave very frank answers, I didn't get the feeling that they were trying to "sell" the school. All the students I met were genuinely happy and mentioned good points about the school that they genuinely loved. My overall impression of the school was positive and they exceeded my expectations. The only real downside of the program that I gathered was the amount of research in the medical school. Quality wise, I don't think they lose out, but they simply don't have as many faculties doing research as the more established schools. So you are out of luck if no one is researching in the field you are interested in. Of course, if you are considering Caltech then the story is different. That being said, the school is determined to climb to the top and is hiring new faculties every year, often big names. In fact, many of the faculties I met were recent recruits. It is also the students' unanimous opinion that the administration takes their feedbacks very seriously to improve the program, and they had plenty of evidence to back it up. I think to summarize my impression of the school, I would say they are truly a school on the rise, with a determined administration and more than enough resources to pull it together - tangilbe improvements are already in place, and every year (well, according to some students, every semester) they are improving more.