Congratulations! I haven't interviewed there but lived Mobile for a really long time. The Homewood Suites (530 Providence Park Dr E, Mobile, AL 36695) and Hampton Inn by Providence Hospital are in a good spot, good area, and are really nice. Really close to South Alabama and you can walk to a couple of restaurants (Friday's and Bone Fish Grill). I have had family stay at the Homewood Suites and they really liked it. I would avoid staying anywhere off the Interstate. Right now it looks like you will spend about $87 a night at the Homewood Suites. Whereever you stay make sure you give yourself plenty of time to drive to South, the traffic on Airport Blvd. can become really insane sometimes. Are you interviewing in the College of Medicine building or the Central Services Admn Building? I visited there before and Google Maps had the pin in the wrong location for the medical admissions office. Make sure to do a pre-drive the day before. South's campus can be really confusing sometimes.
If you want to stay for a bit and see downtown the Renaissance Mobile Riverview Plaza Hotel downtown (64 S Water St, Mobile, AL 36602) is super nice. My wife and I stayed there after we got married before going on a cruise (about $120 a night I think). It overlooks the bay and the rooms have a lot of windows.
I have been accepted to another medical school but really want to interview at South Alabama. I have to accept or deny the other medical school by December and there is a huge non-refundable deposit for them due at that time. I hope I hear about an interview or rejection from South before then so I could make an easier choice but I hear they interview all the way out to March or April.