I remember this exact question was asked a while ago but I'm not sure how reliable the archives are now. So, doing cardio at moderate intensity (i.e. not killing yourself) should actually benefit you because it pumps blood into your legs which should aid in recovery. After a really intense leg workout you may want to lay off if your legs are so sore that walking hurts. I guess it's a judgement call, just don't go overboard and push your legs too hard. That's my advice.