I had a 2 weeks off leg training a while ago, then decided to make up for it by smashing it really hard, 2 days later i could barely walk, tried to do some cardio and it just made it worse.
If its that bad then you need to let it rest.

But if its not too bad then cardio is good, just don't go to hard.
Personally i finds that the extra fitness i get from a few sessions on the bike each week helps my leg training sessions.

I would limit it to "light" cardio and at least a day separating it from the legs workout.

What type of cycle are you on? Tren and/or dbol kill my cardio.

I agree with nitrogains, if you are going to do cardio give it a few days. If your not cutting don't do a lot of cardio. You should be able to control body fat with diet not cardio. For maximum amount of leg growth do very little cardio (moderate to light pace, low impact) No RUNNING and just keep your diet tight... really want legs to grow, fuck cardio. Train em like a beast, up calories and Split legs different days hamstrings/ quads, calves.

My $0.02 is to give my legs two days of rest after leg day so that the muscle can rebuild.