There’s definitely a Spanish trend right now, and I must say I’m loving it.
Regards learning Spanish solely to understand music, I’m not convinced it’s worth it to be honest. I’m doing AS Spanish at the moment, and I got A* at GCSE, but I still find Spanish music quite hard to grasp (and I listen to quite a bit of it). The lyrics are usually pretty fast, the pronunciation is often bent to fit the melody and the grammar sometimes gets modified too to preserve the rhyming and syllables. Quite a few times now I’ve found myself asking my Spanish tutor about certain grammatical structures I’ve encountered in music, and she usually tells me it’s a stylistic choice to fit the music, rather than an example of good Spanish.
So in short, I’d only recommend learning it if you have a genuine interest and commitment to the language.