I've been there twice - but not in peak season.
Went in June with DH and DS then later that same year in the November with just DH.
It is quite a nice resort - enough going on. Some nice beaches. Easy to get there on the train from the airport. Frequent buses too.
We stayed in the Carihuela area, which is perhaps less busy? But this was a few years ago now, so I don't know.
Weather will be great in July for you.
Have you had a look around on TripAdvisor forum for Costa Del Sol ? You'll pick up some good info on there.