Translation:I eat lunch at the cafeteria.
The meaning of "cafeteria" changed with the borrowing from Spanish into English: https://en.wiktionary.org/wiki/cafeteria#English. Apparently, it's a U.S. term; in Britain they call it a "canteen." That's used in U.S. English too for something similar, but sounds like military lingo. Normally, a canteen is a container for carrying water while hiking.
"Refectory" in English is a word almost entirely restricted in use to monasteries.
is there a reason why the polite / honorary ‘o’ is used when talking about lunch (ひるごはん —> おひるごはん), but not breakfast or dinner? ... or is also ok to say 「おあさごはん」 and 「おばんごはん」 ?
the only reason that comes to mind is that in modern society, people mostly eat breakfast and dinner at home but eat out for lunch so maybe they want to use the polite term, since they may be discussing lunch with colleagues or strangers. i dunno.
good question. the お in this sentence is the “polite o”, used to turn「ひるごはん」 into the polite form of “lunch” - for when you are talking to a stranger, superior, or client or if you’re someone’s guest, for example. kind of like saying 「お名前は何ですか？」(onamae wa nandesuka?) to ask someone’s name and show that you politely would like to know, as opposed to questioning them or diminishing their name.
the を in this sentence is also pronounced oh (the ‘w’ is silent) and is a grammar particle used to mark the direct object of the sentence, or the noun receiving the action of the verb.
the を particle always comes right after the noun and right before the verb in japanese sentences. for example, 「おひるごはんを食べます」 (ohirugohan o tabemasu - “i eat lunch / i will eat lunch / i am eating lunch”), 「ビールを飲みます」 (biiru o nomimasu - “i drink beer”), 「机を買います」 (tsukue o kaimasu - “i buy a desk”).
there are more details about the を particle in the lesson tips.
hope this all makes sense.