I started back doing bikram yoga within 2 months. I started slowly, and was very careful with the postures, modifying alot of them, but then as I gained strength and flexibility I started being able to get into them better and better. I did bikram yoga about twice a week up until the surgery, so I was anxious to get back into it.
I am still going about twice a week, still modifying certain postures (standing head to knee can only hold my knee, have problems with the floor version as well), and use blocks when necessary. Recently I have backed off a bit because I have been having alot of pain and lack of flexibility in my hip area- I think due to a build up of scar tissue. However, the yoga is great for improving overall flexibility, even if you have to modify the postures significantly. Hopefully you have a studio to practice where they are not really pompous about people not doing "straight bikram" and modifying and using blocks where they need to.