@Amir: Why is it different? Isn't learning grammar about understanding and applying the patterns that help you construct valid phrases?
More importantly, if mathematics can be used to teach computers to process language and translate a large text from one language to another, why can't mathematicians do the same? After all, natural language processing (NLP) is nothing but a combination of mathematical tools and linguistic theories.
As a math student, my opinion might be biased. But I have noticed that mathematicians can explain their ideas in a foreign language clearly. I believe mathematicians understand grammar well and get used to it soon. But it doesn't mean that they can speak English (edit: or a foreign language) better than others. After all, speaking a language isn't only about the grammar, but it's also about the vocabulary.
Some famous mathematicians were polyglots. It is said that Gauss could speak more than 10 languages fluently before the age of 18. Euler too was a polyglot. Most of the important mathematical works in history have been written in a language that was different from the native language of the author. So, in my humble opinion, the answer to your question is positive. :D
One interesting fact about mathematicians is that when they read a math article, when they want to read numbers and do calculations in their head, they always do it in their native language. I don't know why. But it's probably because it's easier to think in your native language. :P
"So, knowing only 135 words (including prepositions, (in)definite article(s), etc.) is enough to understand half of Brown Corpus which contains 500 samples of texts in English with over 1 million words!"
That reminded me of a joke:
Physicist, ingeneer and mathematician were suggested to fence as many as possible cows with limited quantuty of pickets.
Physicist said: "I'll make a square yard, with a distance between pickets lesser than a cow's breadth, cause it's area is the largest possible."
Ingeneer answered: "I'll make a circle yard with crossbars, cause it's strength will be the most possible."
Mathematician fenced himself with few pickets and said: "Assume I'm outside."
I thought math was a foreign language.
But seriously, I think it's much more important to be comfortable with not being 100% certain of anything.