We are going in late July and would like to go to BB or TL about 3:00 p.m. How are the crowds by then? We have always gone at park opening time to get a chair and left by 2:00! How late do they stay open?
During the summer the parks are usually open until 7pm. Anyhow, as you said a lot of people do start to leave between 2-3pm. So you should be fine, as opposed to getting there around 12-1pm. I think you'll be able to find a spot by then.