In the past, I've shown up at the Epcot resorts during very busy times (during F&WF, when there was a giant IT conference going on at the Epcot resorts) and saw similar signs about limited parking. The guard wouldn't let me in to self-park, but as soon as I told the guard that I would valet park, he would let me right in.
Thus, I would suspect that a sign indicating that there is limited parking applies only to self-parkers and not someone who wants to valet park.