I speak English only, and even that with an Australian twang.
The more I live in England, and the more Continental Europeans I meet, the more I realise that linking intelligence to number of languages known is non-sensical.
What, every child in Continental Europe has an intelligence of 13 or above because they can speak English and their native tongue?
I think this reflects the ango-centric nature of the rules. Maybe in the USA (not Canada you lucky guys and gals), the UK and Australia you have to be pretty bright to be offered the opportunity to learn another language at school. But not so for vast areas of the world, where bi, or even try-lingualism is the norm. What everyone in Switzerland has a 17 intelligence (+2 languages) in their tri-language country?
I don't think it's even historical in England - French and English being commonplace in England during the middle ages, not to mention those that also knew Latin. Every vaguely educated person = 17 intelligence, I don't think so.
I suspect, assuming a basic intelligence, that number of languages spoken is cultural rather than intellectual. Perhaps languages known should be campaign driven rather than ability score driven? Social standing is probably a better guide to number of languages known, than one's intelligence score.
Intelligence might be used to modify speed of language learning?
You travel somewhere, how quickly do you pick up the lingo? Depends on your intelligence score.
Every week roll to advance, modifying roll by intelligence score. If fail, add +1 to roll for each subsequent week, until advance to the next level.
Level 1 = Tourist (starting level) Où sont les toilettes ?
Level 2 = Rudimentary (Requires 1 on a d6 to reach)
Level 3 = Conversational (Requires 1 on a d10 to reach)
Level 4 = Fluent (Requires 1 on a d20 to reach)
Level 5 = Native (Requires 1 on a d100 to reach)
Additionally, or perhaps, it is time to abandon the link between intelligence and number of languages known, and use it for XP bonus.