It was really too hot for us last year, we went in July. But as others have said I think that last year was more hot then usual!
We live in Nevada and were used to dry heat! Anaheim is not the same kind of dry heat. I mean we can actually feel the moisture in the air when we breathe while were there! So it's not quite desert dry for us! Last July not only felt hot, but it also felt humid. We've gone one time before in July and it wasn't quite that bad. So I think last year was just out of the norm hot.
But honestly I prefer early June, so I can get the more mild "June gloom". Or fall, like were doing October this year. I don't do well in hot temps!