Very few opera houses offer subtitles. This is because subtitles near or on the stage would be difficult to read due to the heads of those in front of you. So

Very few opera houses offer subtitles. This is because subtitles near or on the stage would be difficult to read due to the heads of those in front of you. Some (e.g. Vienna) have a seat-back system that shows subtitles. Surtitles, on the other hand, are pretty much ubiquitous.