I'm sorry to hear that man.
everyones different, depends on the type of injury, what graft they use, any related damage and how good of condition your in now. if you don't have any cartilage damage your much better off than i was. I tore my snowboarding in february 2010, was messing around on the wakeboarding/wakesurfing by mid-end of season that year.
rehab, rehab, rehab... take it seriously and do 110% of what they tell you. as far as the knee, i'm back as much as i can be but i've also seen people who never bounce back from it: mainly due to the poor training they did after the injury. I would expect about 4 months before you can start wakesurfing, 6 months before wakeboarding and really being back 100%... probably about a year