We got there right as the park opened and made our way there first thing. We got our pick of any of the loungers, and the attendant let us know which area receives sun during what point of the day along with where we should sit if we didn't want any sun at all.
I would say the area was about half full the day we went. There were never more than a few people there though at any one time (I doubt anyone really stays there all the day, this is somewhere to come back and relax periodically throughout the day) and the area is fairly spacious. There are likely to be more people there now (we went in late May), but I doubt it would ever be overflowing with people, even if all the loungers were sold.
I hope this helps!