Oooh now. I had this operation in July (along with cartilage repair) and it's 6 months for us normals, probably half that for someone who isn't a fat office worker.
This. I've just had a partial menisectomy and meniscus repair.
There are 2 things you can do (or both at the same time like me). If it is a small piece that is damaged, or it is in the inner section of the meniscus (which gets no blood and thus cannot heal), then you can cut it off (menisectomy) and you're walking in a week and back on the pitch in 6 weeks.
If it is a significant tear, and on the outer section of the meniscus (which gets a blood supply and can heal) then it is a meniscus repair where they stitch, staple or anchor it together. This will take a long time to heal, as you are not even allowed to weight bare for 6 weeks. It would take him 4-6 months to get back to action.
So it depends on what they (he) decide to do. He's 29 which is still considered relatively young, so they would probably favour a repair as that is the better long term option.