I've seen a few discussions here of people wondering if they should book lessons with teachers from X country, because they've heard people from X country speak too fast/use too much slang/etc and thus you should avoid them unless you're an advanced learner.

Actually, in every single country there are both educated people who speak very clearly and avoid slang, and people who speak in an almost incomprehensible way, even for other natives! This happens in every language.

I believe a key factor in your ability to speak clearly is whether you have frequent contact with native speakers from other countries. For example, if Pedro* from country A has friends from countries B and C and has traveled a few times to countries D and E, he might have become aware of his own accent (Everybody has an accent; otherwise you would sound like a robot), and thus can make an effort to reduce it while speaking with foreigners. Pedro might have also noticed which words and usages might be unique to his country or his region, and has also learned to swap some of his local words for other more internationally understood ones when needed. Instead of thinking that his way is the right way, Pedro has learned that there are many different ways of speaking, cooking and doing things, and that his way is just one of many. Pedro now knows his own country's customs, food and dialect are weird to people from other places, and he's OK with that. He understands his own language is pluricentric and thus there is no single city or country that can be considered "The standard".

Of course, not everybody ends up being enlightened with his contact with people from other countries: For example, if Saulo* is also from country A and visits countries B and C, he instead finds in these encounters and travels further "evidence" that his way of speaking is the only correct one and that he "has no accent", while everybody else does. Saulo thinks "Why is everything so weird here? Why can't they even make proper food?" when he travels, instead of reflecting on how weird his own ways might be to people from other countries. What's even worse, since Saulo has never reached a near-native level in a second language (Which is probably the case of 99.99% of native Spanish speakers), he might truly believe his native language "Is the most wonderful language in the world because it's the only one with which you can express any thought with precision". **facepalm** (Yes, I've heard several people say this). We all have friends like Saulo. Actually, most of our friends are probaly like Saulo and very few, if any, is like Pedro.

The difference between Pedro and Saulo is known as Cultural Awareness, and is now seen as one of the most valuable skills in this era of globalization. So, my advice is this: If you're traveling to a particular country, don't be afraid to book lessons with teachers from that country: They can help you plan your trip, and might offer advice on food and places to visit. Beware of teachers who closed-mindedly think "they speak in a standard way because they're from country A", because that attitude might be contagious. Instead look for people who are culturally aware, preferably those who have learned other languages to near-native levels and show appreciation for other cultures.

* Ficticious names.