True, the term 'Mayan culture' is a very broad one. It represents a large number of tribes in a large area over a very long period of time. So to say the ppl in this movie are Mayan is misleading.

However, from what I have gathered the movie is quite accurate in it's portrayal of these human sacrifices.

I posted a review of this movie earlier. Mel Gibson said of the movie..."The precursors to a civilization that’s going under are the same, time and time again... What’s human sacrifice if not sending guys off to Iraq for no reason?"[/wikipedia] He is comparing the human sacrifice of sending the young to die in Iraq to the human sacrifices of the 'Mayans' who also sacrificed their young. All ancient cultures have practiced this. In Gibson's mind, war is a modern day human sacrifice not so unlike the literal human sacrifices of the 'Mayans.'