In my opinion Business Management is a very competitive market,both in US and Canada. Where ever u decide to go I would suggest you to select a stream that is closer to ur Bsc in physics to produce a good SOP and do event management based on opportunities that becomes available (since you have experience back home u might get some good offers and as u grow u can decide based on that).
As far as I know most of MBA program require a 3or 4 yrs bachelors degree, arnd B+ average and money (its pretty expensive here). If u have these u can do it anytime . I dont think Pg diploma is a requirement