having relocated for a while from switzerland to indonesia for the fun of it, i, too feel the same doubts: is it ok to express negative thoughts / impressions / observations to locals? you don't want to be the one always complaining and especially when going from a more to a less developped country, you constantly have an inherent, well, lets call it "shame" anyway for being in a better position and having more choices available through less effort for no good reason. so the last thing you want to sound like a teacher.

but in fact, i remind myself that, back in switzerland, i have changed, improved actually, thigs in my life, even if small and not too important, inspired by friends who were telling how this or that is done differently, or better, in their countries. so i really think it's perfectly fine to be honest about disliking the local coffee, if you from time to time also express your euphria about your host country - and i am sure there is plenty to be euphoric about.