I was admitted last year (but will not be attending) without AP classes. If you're really that worried, nothing is preventing you from taking the actual AP exams. I took the AP Chemistry exam and scored a 5 on it after taking two years of regular chemistry with lab. I felt really confident in chemistry and it was my favorite subject, so that's how I demonstrated proficiency. Also, I didn't do this, but you can take the AP Calculus exam if you feel good about your math skills, as most MIT freshmen (correct me if I'm wrong), have some sort of AP math credit since it's a math/science-centered school. The AB exam isn't that difficult (only Calc 1, which is mainly differentiation).