All the complaints about the bad Spanish are kinda uncalled for.
I'd say.
Remember that the author most probably did their best with what little they knew about the language. If a manga or anime used my native language, I'd be over the moon, regardless of how "badly" they use it.
I'm a native Spanish-speaker, and this I can tell you: the Spanish in this manga is not bad. I spotted a grand total of four mistakes:
1) One time, she uses the Portuguese word for "I" instead of the Spanish word.
2) One time, she uses the Italian word for "awesome" instead of the Spanish word. (And she says it like she's talking about her instead of the situation: "you are awesome" instead of "this is awesome")
3) One time, she says in good Spanish "Did you wake me up?" but actually she was trying to say "Did I wake you up?"
4) One time, she says in good Spanish "I like this!" but actually she was trying to say "I like you!"
And then there's her final outpour at the airport, which is quite choppy and incoherent... but I'm not counting it among the mistakes because I suspect it's supposed to sound like that -- the result of her extreme distress and confusion, intermingled with sobbing.
On a slightly different subject, one thing that made me feel a bit disappointed is that we never meet the people from Cebu -- I mean the inhabitants, the Philippine people. We have a Japanese girl and a Spanish girl, and they talk to each other, sometimes in Japanese, sometimes in Spanish and sometimes in English... but we never find what happens when they try to talk to the locals. I wonder how they would fare?