Hi

You probably could start flowering it now if its been growing for over 2 months. Also, to answer your flowering question, 8-11 weeks means it will take that long to flower before you can harvest. It all depends on what strain you have.. sativa or indica. Sativa takes longer.
But the best way for you to know its time to harvest, is to check the trichomes with a microscope.
Best advice though is to start reading up!!!!!

good luck!