Can I talk to the actors?
You should never approach the actors. The set is their workplace and a professional environment and should be respected as such. They have a lot going on in the scenes and often their time between takes is spent preparing for the next scene. In some situations, supporting artists may be removed from set if they inappropriately approach actors.
On the other hand if you are approached by one of the actors, always be friendly and engaging, but keep it professional.