We have not really had a problem with this, even on sea days. Of course there was always the few people that put stuff on their chairs not to return for several hours, but, especially by the Mickey pool people tend to not stay too long. We were able to obtain front seat chairs within a 1/2 hour of arriving at the pool in most cases. Maybe we just got lucky, but just keep your eyes open and you should be able to catch an open one.
Kathy