Status, humility or strategy?

For one reason or another, a significant number of people I've worked, or interacted or had more initimate relationships with during my life have not spoken English as their first language. It can be demanding and sometimes difficult as a listener (or reader), but I've mostly found it interesting and rewarding for the insights and clues it gives you into other people's way of thinking (which comes out as they "see" another language being spoken) and it's often creative in the mix of words, concepts and tenses that people use.

This puts me in a bit of a conundrum when well-meaning Portuguese friends and colleagues urge me to write (informal) e-mails in English, not Portuguese. Writing them in English, they tell me, looks more educated than writing in Portuguese with mistakes. Someone who writes in English maintains their superior position, whereas writing in Portuguese as a second language puts you in an inferior position in relation to people who write it correctly - and you risk not being taken seriously.

So, do I stick to my principles and enter other people's world's - creatively using their language, but at risk of being looked down on? Or do I stick to the language I know best and maintain my lofty status?