Some medical sites said it takes four months but other sites say that a full recovery in four months is nearly impossible. It really just seems to be a case by case basis on how your body reacts. One site sad that the surgery performed in patients under 45 have a 75 to 80 percent success rate.
The most recent high profile surgery was done on Amare Stoudemire from the Suns. He had it done in October 2005 and returned in March 2006. However, when he came back stiffness developed in both knee joints (other knee was overcompensating for the injured knee) the team doc decided he needed more rehab time and didn't return until the 2006-2007 season. But when he came back he played to his old form.
It seems Vilma should have enough time to rehab, but he will need to get through it mentally which is easier said than done.