I have gotten the quest Caesar's Favour once already, but will it re-occur if I have neutral reputation with them? I'm wearing the Centurion's armour and it resets my reputation with the Legion to neutral, so would I have to wait 3 days while having positive repuation with the Legion in order for the quest to re-occur?

Here is all you need to know but weren't afraid to ask http://fallout.wikia.com/wiki/Caesar%27s_Favor