Hi,
My friend is staying here in july and was worried about it after reading some bad reports on it.
I was in Salou last week and went to have a look at it for her, it is roughly 15 mins walk to the beach, its just off one of the main streets in Salou. I went and had a look in the restaurant/cafe and also at the pool and it all looked fine, clean and tidy. I also asked 2 different people who were staying at the apartments what it was like and they said it was fine, the rooms are basic but kept clean. The only bad thing that both of them said was to be careful about which block you get because one of them faces a nightclub which stays open til 5 or 6 am. This may not be a prob for you if you intend to go there yourself
I am not sure what the weather will be like for you as i have never been at that time of year.
You will be able to find out about the water park times here,
http://www.portaventura.com
Lou.