I went through this once. Had a spiral fracture of the fibula and all the ligaments torn out. Yes, it hurt. But I could still drive a clutch.
Don't do it on drugs. Let somebody else take you. Also, make sure you have sufficient room to move you feet around before you start driving. You don't want to get your cast stuck under the brake pedal.
My biggest mistake came on the day I had the cast taken off. I didn't realize how much it would hurt to move my ankle around (the joints were frozen after 2 months in the cast), and I had forgotten to bring a shoe. I tap danced between the clutch and the brake with one foot that day, and I don't recommend it.