It appears that scapeuse's response is the most reasonable and accurate.
Last night I spoke to an uncle of mine from Spain, who speaks French, Latin and Greek, but not English (he's got a Phd in philosophy). He didn't know what a checkout was, and I laughed when he told me. Supposedly, everybody is learning English nowadays and you can talk to them in English, and hopefully they'll understand you, but if you want to speak Spanish, and you say "Where is the toilet, please'", you'll probably be understood, and they'll point you to the toilet. Excellent Spanish! What a success! Hold on, that's not Spanish. How is it possible? What happened is that the Spanish natives people will understand some English, they won't correct you, and you'll get away with it thinking that it is Spanish. Also, most Spanish native have an inferiority complex when it comes to languages, and they always think that if it is English, it is better than Spanish. So, why bother learning Spanish anyway? Better news than scapeuce'! You can not only "checkout time" in Spanish , but also "what" an "is" to ask "What is the checkout time'" in Spanish! Modern Spanish doesn't get any easier, uh? Try it! They'll understand your "Spanish".
Ask "¿A qué hora hay que dejar la habitación'", and you'll be understood by 100% of Spanish natives, as it is Spanish; ask "¿Cuál es la checkout time'", and every now an then, you'll meet someone whose English is not good enough to understand you (surely this won't happen in 5 star hotels, but in rather smaller and cheaper ones). By the way, is it "el checkout time", or "la checkout time"? I cannot find this word in the dictionary. I wonder why.