Can you help me come up with some good questions to ask the dean of a medical school in a casual interview?

If I were you, I would just ask the questions that you have on you mind. Then ask the Dean why you should go to their school!

You should focus more on what questions he/she will be asking you!  It's an interview - they ask you questions and you should be prepared to give answers to questions like, why do you want to go to medical school, why do you want to be a physician, what do you think about stem cell research, abortion, genetics, bioethics, health care, standard of care, boutique medicine, etc.

I asked what they (my interview panel) thought was the biggest weakness of their school and what they were doing to improve it. Depending on how big the school is-how do they keep the quality of education high and to standards. Are you interested in have a rotation abroad? Do they offer any programs that would let you? What reasons do they hear for why people did or didn't chose that particular school? Are you interested in clubs or electives? What ones are available that would suit your interests?

It may not be as casual as you think.( this would be in bold type if I could do it )  I would think it inappropriate for a possible applicant to be asking the Dean of the Medical School if his is a good school.  What answer would you expect?  Rather, I might explain why I want to go into medicine, and why I am interested in his school.  And do not mention "making a lot of money", or you will never make it to the formal interview. It is OK to say there is a certain stature in the community which you think you would like.  You might ask his advice as to any additional courses he thinks you could take to properly prepare you for Medical School.  
Tell him about your hobbies, your outside interests, your volunteer work, if you get the chance. Let him lead you into the conversation.

Remember you are trying out for the BIg Leagues- this is not college.
You need to be well spoken, literate, thoughtful. No stupid answers.  Engage brain before opening mouth.

Few medical students pay attention to where they'll do their second two years of medical school (Clinical Rotations).  Most assume it will be done at the school or the affiliated medical center.  But there are many schools that do not have medical centers or medical centers that are green book for all of the core rotations, much less the elective rotations.  So, my first two questions would be where would I complete my core rotations and whether the school assists in setting up my elective rotations and what those affiliations are.

Another question I would ask, especially if the school posts its 'ranking' on its web site is whether the Dean participates in the US News and World Report ranking survey and if he/she did, how he/she explains the decision to participate when the AAMC has asked all schools not to participate.  If he/she did participate, I'd want to know how a reliable and objective opinion could be formed about over 127 schools.

Another question I'd ask is what the school is doing to address its attrition rate.  Since most people drop out of school in the first semester due to academic difficulties, what support does the school offer?