I don't think whether an audience is primarily consisted of tourists or not really determines who gets voted for what. If that were the case, I would think Bazzard would get voted for everything all the time, as the author is constantly suggesting that the audience vote for him, as he is "longing to play a larger part". I think Helena might be a less obvious choice, and Rosa certainly is a less obvious choice for murderer. With that logic, Neville and Jasper should be voted as murderer every night.
I actually saw Drood last Wednesday night with what seemed like mostly tourists in the audience, and Crisparkle was voted murderer.
Meanwhile setting next to me were obvious fans of the show, and they were clamoring for Rosa to be the murderer, because that is their favorite confession.
Who really knows?
"Someone tell the story...Someone sing the song...."