You could, but it wouldn't be easy, and your MCAT score would probably not be quite as good as if you had the physics courses. I'm in a similar situation (I placed out of the first semester of college physics in high school and haven't taken the second semester) and just took the MCAT and I can tell that even though I studied physics a lot to make up for it, I think having taken that second semester would've improved my chances at scoring higher. That being said, if you really wanted to you could start now and if you're diligent, you would probably be ok by July.