Visible crew/equipment: Towards the end of the movie, the Predator is climbing up the side of a tall building. Danny Glover jumps in his car to take off after it. As he starts to drive away, towards the left you can see the shadow of an elevated cameraman/equipment. (01:03:55)
Visible crew/equipment: When Jerry is fighting the Predator in the subway car, watch closely behind him when he runs out of ammo. He bends over to pick up a knife, and you can see two distinct shadows on the wall in the strobing light. One is his, and the other belongs to the camera man standing a few feet to the side. (00:57:45)
Visible crew/equipment: Near the beginning of the film when the police car explodes and flips over, you can blatantly see stunt wires used to aid in flipping the car. (00:02:45)
Visible crew/equipment: When the Predator is attacking the Jamaicans in the penthouse, you will see the guy who gets pinned to the wall with the net propelled backwards. We are led to believe that it is the force of the Predator's weapon - not so - it is the bungie cable attached to his trousers. (00:24:55)
Answer: The predators are honour bound hunters, and as such they will only attack a target if it is capable of defending itself (i.e, if it is armed, which is why it doesn't attack the boy in the cemetary). Although the police outside were armed as well, the Predator presumably attacked the drug dealers because they were a harder target (as the police were outside he could have just sniped them from the roof tops, but he had to get relatively close inside the building) and as such, killing them gave a higher honour. The obsession with Danny Glover's character is probably because he is quite a brave and heroic person, similar to a Predator (the way he saves the other cop by risking himself etc.), so the predator may have been studying him for a while. There's also more honour in killing someone like that (as he'd be a hard target) than there is in just killing a random armed guy.
Gary O'Reilly