AMC and Cinemark theaters have recently made statements that they are banning masks, helmets, face painting and (fake) weapons of any kind at their theaters. Regal Cinemas limited these items after The Dark Knight Rises theater shooting in Aurora, CO a few years ago.
AMC's website tells customers, "AMC does not permit weapons or items that would make other guests feel uncomfortable or detract from the movie-going experience. Guests are welcome to come dressed in costume, but we do not permit masks. In short, bring your lightsaber, turn it off during the movie, and leave the blaster and Darth Vader mask at home."
Cinemark, via posters advertising the December release states;
"Star Wars costumes are welcome. However, no face coverings, face paint or simulated weapons (including lightsabers/blasters) will be allowed in the building."
Moral of the story is - if you plan on dressing up - check your theater's policies before coming decked out in your Star Wars cosplay finest to make sure you are within regulations and can enjoy your movie experience without conflict and disappointment.