I don't think it makes a difference, at least nothing drastic. I've heard stories about how football coaches would make the whole team watch porn before the game to get thier hormones raging lol.
For me if I have sex before the workout, and I have for years, sometimes it drains me and sometimes it takes the edge off and releves alot of stress. I've broken prs and ive had to go home because my performance was garbage. All in all I feel a healhy and regular sex life is optimal, but that's just me. I wouldn't have sex the night before a big game or event though just to be on the safe side.