My OB's always said 6 weeks, just to let everything recover from the shock it goes through with the operation. The scar is fully healed at 3 months, so you should be able to do everything by then, if you have no complications.

I was up and exercising pretty quickly after my first one, but had an infection in my uterus the second time round, so I never really got back into exercising before falling pregnant again when DD1 was 7 months old.