I actually spoke to a CRO CM about this. It seems that most people either go at the beginning of their summer, at the end, or around the 4th. According to the CM this makes the middle of July the slowest. Also a lot of people that go in the middle of the summer go for a long time, a week or two, and tend to take it easy and spend more time in the resorts. That doesn't mean that the place will be deserted. It will still be packed. Just not as packed.