If you really have your heart set on USC or any post-bacc program with stat requirements higher than yours, you're going to have to bring your GPA up on the side with classes at a local U. If the programs are strict with their requirements, that's pretty much the only thing you can do.
Have you not had all of your pre-med pre-reqs given your major? USC is for career-changers, and you have to have not taken the pre-reqs, as those are pretty much the only classes that their program offers. I would think Molec. Bio would've had most if not all, but then again, I wasn't a Molec. Bio major, so...
I've seen some post-baccs on the AAMC website that have stats lower than yours; you might want to look into that. I've seen some as low as 2.7. I don't know, however, if those programs are only limited to disadvantaged students.