Originally Posted by
JMN57
Depends on where you are sitting. If you are in the Poltronissima (and particularly Gold) the patrons will generally be better dressed although there are always a lot of tourists and it is summer so I wouldn't say that is a constant. If you go back to the gradinata (stone steps), it is much more casual with people picnicking, etc.
Personally, I wear trousers, polo shirt, sport jacket, loafers without socks and I am comfortable both temperature and style wise (and I generally sit in Poltronissima Gold).
That first paragraph seems to summarize pretty well what I've seen when there for the operas. If going for the stone steps, you may want to bring a cushion upon which to sit -- that or buy the inflatable ones there. Personally, I like the "stone steps" because it just feels more time immemorial.