if you saw HBP and didn't read didn't you think that dumboldor was somehow still alive?

I have to say that I disagree with you. Because besides the fact that I had read the book first, there was enough hints to say that Dumbledore was dead, regardless of whether or not the viewers knew that "Avada Kedavra" was the killing curse.
Even though Dumbledore's funeral was cut out of the film, for who knows what reason, still the Dumbledore farewell scene should have given all viewers the message that the headmaster was indeed dead. The acting wasn't terrible and it certainly was good enough to portray the scene. The movie gave us no reason to believe else wise, it dropped no hint that Dumbledore was indeed alive. I think that the Snape and Harry shouting match (which thankfully was in the novel as well) also confirmed Dumbledore's death. And if even that left a viewer hanging the farewell scene definitely wrapped his death all together. True, I agree, that the death of Dumbledore was sloppily pieced together and did far from justice to the emotional impact readers felt from the book. I agree it left people hanging going..."What he's dead? That's it?" I suppose you could argue that this could cause people to think he really was alive because of how the movie portrayed this particular aspect of the book. Still, I believe that there was no proper purpose for a viewer to feel as if Dumbledore was indeed not dead, and would be alive in the final films.

I saw the movie before reading the book and I thought he was dead. However, my Dad was in denial, and he thought that Dumbledore had to fake being dead for this big plan that he never explained. But, I thought he was crazy, haha.

No, it was the killing curse, they explained even in the movies that Avada Kedavra was the killing curse.

No.The way the scene was shot and how he fell slow mo was definitely a gone for good sort of deal.Also that Harry didnt immediately run down to him to check if he was okay before chasing Snape down like "What the Hell man?You nearly killed him"