brazilians would be considered latino as well, along with spanish and french speaking latin americans. latino generally refers to americans from countries formally colonized by latin speaking countries, mainly spain, portugal, and france. certainly, english speakers from belize, for example, and dutch speakers from curacao or guyana might consider themselves latino as well, not because of language, but because of regional ties, similar economic histories, etc.
but i agree with you supermoni that everyone has the right to identify themselves appropriately. however, i wouldn't advocate streching one's identity to try to fit neatly into one of the five main categories, or so. portuguese sounds sort of exotic, but is it really different than being german, french, or italian? i think the other box is the way to go.