serenade,
i wrote advice for you in the other ochem + physics thread
yes if you finish pre-req's by end of sophomore year, you will have time for mcat prep your junior year. But there is no need to finish them by beginning of junior year. You should have them done by end of junior year.
I would take physics my sophomore year, and do orgo my junior year if I were you. Dont take anything over the summer.... but if you decide to do both your sophomore year, and prepare for MCAT your junior year that works too.... buy berkeley review prep books for MCAT in all subjects... bio,chem, orgo, physics, and english and master them throughout your junior year while taking non-time consumptive classes... do well on the MCAT... and take those upper-level science classes (which i didnt have to take cause i am a non-science major) in senior year....