Probably because I'm an old fuddy-duddy, I tend to view 'full literacy' as being a skill rating - rating - of the average INT + 2, or 5. That'll result in a pool of 8, sure, but when you get down to it, it isn't a matter of 'what your Pool is', because there are two basic stages you have to get through: hearing (or comprehension), and speaking (or communication).
When it comes to comprehending a language, you get your pool - INT + Skill. A high intuition means you have a great chance of comprehending what it is your conversational partner means, whether by body language, gestures, vocal inflection, or whatever. Even a low-skilled individual (or a no-skilled individual who gets lucky) has a chance of understanding something quick and basic, such as 'stop!' or 'duck!' The more complex your conversation gets, however, the higher the threshold for comprehension is, and thus the less likely you are to hit it reliably with your scintillating intuition; there are words in languages that aren't commonly used, that are used 'differently' by certain sub-cultures or different nationalities (English and American, or virtually any of the different South American Spanish-speaking nations), or that are simply unusual or infrequently used. Even a native speaker can run into unusual or technical words that they don't understand and need explained to them, but it's easier for them to ask, and when it comes to most conversational gambits, one isn't liable to get lost in the screwball mystic realms of linguistic dark corners. In short, if all you're doing is listening, then if you have a high Intuition, all you really need is a 1 or 2 in the language.
Which leads us to speaking - communication. This is where subtleties of emphasis, turn-of-phrase, innuendo, and all the other really interesting linguistic tricks live. Your straight intuition isn't going to do you much good, because trying to con the security guard by putting together "Yesterday he go to the bathroom on my name!" (to use Beta's amusing example) isn't going to get you very far - in part because it's tough to be smooth (with a con, with a negotiation, with any social capability) with someone if the words you're putting together could have come out of the mouth of a three-year-old because you still have to stop and think about how to conjugate 'ir' in the third person past participle in order 'estefar' ('to cheat' or 'to con') that Hispanic guard. As a result, having a straight-out baseline for a familiarity with how to actually speak a language - if you've moved the knowledge of all its normal grammatical rules, its 'top 10,000 words', its little exceptional tics, from your conscious mind to your subconscious - is a very, very good guideline.
So just understanding? That 1-2 will get you by. But if you want to speak, be understood, and have a chance at even just casually persuading someone that the Cincinnati Lasers are going to kick the Tenochtitlán Volcanos' asses in the Friday Urban Brawl, having a language skill at (IMO a minimum of) 4 is critical. 5 for more-or-less 'like a native', and as much better than that as you care to get for your high-level negotiation.
To be fair, however, you probably need serious skill (5-6) in only a half-dozen languages in the 6th World, because of the vast spread of business and cultures. English, Japanese, Spanish, Arabic, Mandarin (or Cantonese, depending), and Hindi will likely let you be mutually understood by 95+% of humanity, because beyond the borders of the United States, bilinguality is almost a given. Toss in French and you can probably bump that up by another percentage point or two.