I'm sure it's not set in the present. If it were, they'd call it a reboot. TPTB are pointedly calling it a prequel in all the print descriptions. The sign in the poster is not a modern hotel sign. I'd bet my paycheck it's set in the 1950s. Norman simply couldn't get away with everything he did, including keeping a dead body, in a present day setting. The whole nature of the story, how isolated he is--the fact that no one came snooping around from child protective services even though a well known crazy woman had a child with her....it just wouldn't work in the internet age. Norman could google mental illness.
No, it's a prequel. It's set in the past. And I agree that Psycho II was a good film. It had the saddest music I think I've ever heard in a movie. Google it and it really sets a tragic tone. The more I think about this series--the more I think it could work.