I love this song. It's actually quite difficult to translate the line "las nubes se van, pero el sol no regresa" from Spanish to English while retaining the extremely familiar metaphor and also retaining the poetry.

A one-word-at-a-time calque would be "the clouds go away, but the sun does not return".

A translation that preserves the meaning very well in terms of how suns and clouds work would be this, and it involves adding necessary exposition: "It is definitely daytime, the sun has risen. The sun is in the sky. It was cloudy, there was no sunlight, it was overcast and gloomy. After a few tequilas, the sky becomes clear, but it is not sunny." It is now clear that weather actually does not work this way. If it is not cloudy or overcast, if the clouds have gone away (which is established in the original Spanish), then either "the sun has come out" or "the sun has not even risen".

But this exposes a deficit in the Spanish language: "the sun comes out" and "the sun rises" are usually translated the same way, or it is very tempting to translate them the same way if you don't know English well enough. They both become "el sol sale", which most often means the sun rises above the horizon. The fact that the sun "rising" and "coming out" are different in English is exemplified by the song "Tomorrow" from "Annie", with the line "the sun will come out - tomorrow". The sun will definitely rise tomorrow, and it rose today. But the sun didn't come out today, she had a bad day in reality and it was metaphorically gloomy and overcast. But she feels the sun will come out tomorrow. She knows it will rise, that brings no comfort. She is choosing to believe that the sun will come out after it has risen. And then it will be sunny.

Both song ("Tomorrow" and "El sol no regresa") use an extremely familiar and obvious metaphor of it being either sunny or not sunny when the sun is in the sky (i.e. above the horizon). But both are very difficult to translate into the other language in a way that maintains poetry. And ironically, the translation from Spanish to English is difficult because of the ambiguity in Spanish between "the sun is above the horizon, at least in theory" and "it is sunny and not cloudy". The translation from English to Spanish of "Tomorrow" is complicated for a much more obvious reason: In English, the metaphor is clearly that it might be cloudy tomorrow, but the song declares "the sun will come out tomorrow" with certainty. This is optimism, because the weather is notoriously outside of human control, it is a force of nature. A poorly-done Spanish translation of "Tomorrow" might give the reader the impression that the song says "the sun will rise tomorrow", similar to the final line in "Gone with the Wind". This is a truism. You can say it to encourage yourself, as is the case in Gone with the Wind, but it is not optimistic. The sun rises every single day (except in the arctic and antarctic). So regardless of the weather, or how many people die during the night, the sun will rise tomorrow. (The line in Gone with the Wind is actually "tomorrow is another day", but the idea that she might lose more money or have more family members die between now and tomorrow morning when the sun rises is extremely possible, in the context of the movie. She says "tomorrow is another day" making reference to the fact that a day is a period of having the sun above the horizon, and that will happen again tomorrow. She did not say "tomorrow will be a good day" or "tomorrow it will be sunny" or "I will still be alive tomorrow". Tomorrow is another day, it will occur. So she's just going to wait for it. Tomorrow may not be a better day, but tomorrow is another day, so it might be better. Although she didn't even ask for that.)