The largest problem with breaking stereotypes in a game/setting is if it breaks immersion - basically being seen as either unrealistic or inconsistent writing.
The single biggest counters you have to this is to:
- Make sure there is some reasonable justification from this "deviation from the norm"
- This deviation is remarked on as a deviation by the rest of the world and not just the PC
As for part one, this is where you counter the lazy/inconsistent writing assumption. "I made this one orc a pacifist supergenius just because I thought that would be cool" = lazy writing. Are these goblins from someplace far away, or were they under the heel of some other race that caused their difference?
For part two, if you telegraph some new smarter goblins for a while with other goblins complaining about those "dumb smart-smart goblins that act like hu-mans, they think they're better than us" then you counter the unrealism argument - it's weird, and everyone else darn well thinks it's weird too. That puts PCs in the role of being the ones that can be accepting of it.
Also, make them different enough especially visually - in a LARP type medium it's hard enough to differentiate visuals but "it looks just like a goblin - oh wait it's that different type" can frustrate players; you need a different skin color or something (I had a clan of blue goblins in one 2e campaign...) to mark it.
Not really an RPG example, but recently I've been playing Fallout: New Vegas, where you have several opportunities to interact peacefully with atypical Super Mutants and nightstalkers, and they make use of these techniques so you (optionally) don't just snipe them at a distance when you see a Super Mutant. Most players in 2013 have gotten used to the concepts of factions and variation, so it shouldn't be that hard to pull off.