The runners dont affect the parks, but be aware of the traffic jam around opening time at MK. This last Jan, we got on the bus well before park opening and had to wait two hours on the bus in a traffic jam. When we able to start moving, we were dropped at the TTC instead of MK since the traffic was so bad. I don't know if this happens at all the parks or just MK. We were there in Jan a couple years ago and did not have a problem, but I don't remember what park we went to that morning. If you plan on visiting Universal, this would be a great day to go.