I've been using the South Extension Lot for about 2.5 years now and it works out pretty well for me. It's $60 a month. During peak hours, the buses come pretty often (a max wait of 10 minutes). Between the hours of 10 and 2, it's more infrequent, but you get to know when they are expected. A huge plus is that you also get to park in any med center garage for free between the hours of 6pm and 8am (much better than the hours that you can park in Baylor's front lot as a student), and all weekend. This has been key on clinical rotations, when you have to come in on the weekend, or work a 7p-7a night shift. The front Baylor lot is not always open to students, even during hours they say it should be. Plus, when it's nice outside, you can easily walk from the lot to Baylor in about 13 minutes.
If you're just coming for an interview, though, go with a med center garage - definitely the most convenient.