Okay, Marco Bae doesn't needa know Spanish. Sure, he's Mexican, sure his house has a Mexican inspired style, buuuuut any kid that pronounces horchata with the "h" not silent, probably doesn't know fluent Spanish taut to him by his family, just saying. It might be cute to see him say a few lines in Spanish, due to frustration, but honestly, Star would probably be more likely to know Spanish because of her dimensional hopping. So far, we have yet to see Star's "smart side" and every one has a special thing that makes them smart in their own way, it might be cool if languages is her thing