How long after a patellafemoral replacement are you allowed to drive. It will be on my right knee. I know not while on narcotics...?

Varies. Your surgeon will give you advise on the particular operation you undergo. That would be on your discharge instructions.
Indeterminate. Although this question is more appropriate for an orthopedic surgeon, under no circumstance would it be wise to drive while taking narcotics for post-operative pain.