"¿Cuándo limpiaron ellos los dormitorios?"
Translation:When did they clean the bedrooms?
The subject pronoun can be left out in almost any case. It'll only be included for emphasis ("When did they clean? Not you, I know you cleaned this morning.") or for clarification (ellos instead of ellas or ustedes). The pronouns usted and ustedes will also often be included for additional politeness.
I took a Spanish class years ago at a community college and the teacher, who was from Mexico, emphatically corrected a student's pronunciation of the 'y' sound, for example in 'yo'. She insisted it should be pronounced 'jo'. It seemed odd to me that she didn't bother on discussing accent differences among native Spanish speakers.
Absolutely and also within countries, of course.
I listen to a Mexican station in Mexicali almost all day, the local announcers pronounce their y like j and it is "Meh He Co". It just sounds "wrong" to me when it's said otherwise. But what do I know, I'm originally from New Jersey.
Mexico and their states put out a lot of public service announcements on radio (in comparison to here in Florida) and they do say it both ways.
I'd say from most common to least it'd go like:
- ¿Cuándo limpiaron ellos los dormitorios?
- ¿Ellos cuándo limpiaron los dormitorios?
- ¿Cuándo limpiaron los dormitorios ellos?
- ¿Cuándo ellos limpiaron los dormitorios?
The latter two might have their places switched, but to me personally it sounds grating to have the subject between the question word and the verb.
The different placements of the subject pronoun change the focus of the sentence a bit, but it also heavily depends on how you pronounce the sentence, which word you put emphasis on.
¿Cuándo limpiaron ellos los dormitorios? - Mostly clarifying; ellos is added here to specify exactly whom you're talking about.
¿Ellos cuándo limpiaron los dormitorios? - Changing the topic; we've talked about someone else before, and now we're focusing on ellos instead: "And they, when did they clean?"
¿Cuándo limpiaron los dormitorios ellos? - As I said before, this is more of an afterthought. I want to make sure you understand that I'm talking about ellos and not ustedes.
¿Cuándo ellos limpiaron los dormitorios? - Sounds weird, rather like a relative clause than a question: "When they cleaned the rooms..."
That might be due to how ustedes and ellos are used. With ustedes, you're directly addressing the people that are supposed to do the thing. You can place the addressing ustedes at the end as a kind of call for confirmation. A bit like "alright?" at the end of an English sentence, "did you get that?"
With ellos you're not calling for attention like that because the people you're talking about are not involved in the dialogue. So putting ellos at the end sounds a lot more like an afterthought. But it could also be used as a clarifier to make sure that you're not saying that ustedes should clean the rooms, but ellos. In case there might be an ambiguity when just the verb conjugation is used.