So basically, "por favor" in Portuguese is the same as "por favor" in Spanish?
No please is also correct.
Only in the horror scene described above by Paulenrique.
When you have kids, it's everyday an horror scene. Personnally, I can use it everyday...
I sure hope there is also a heaven scene every day or so in your house! :-)
Being Portuguese and speaking other Latin based languages the expression as stated is in fact correct.
I don't think anyone is disputing whether the expression is correct; it is the translation that is in dispute. "Please, no" is very clumsy English and would probably mark you as not a native speaker.
I agree, "No thanks/thank you" is much more natural in English. We might say "Please, no" under duress, but what we really need to know is whether the above is the COMMON Portugese phrase, i.e. when offered a drink or a sweet.