I find it fascinating to observe how people fake speaking foreign languages. I've been guilty of it myself for sure.
The simplest form of faking it is the "nod and smile". When I used to live in Japan, I learned very quickly that Japanese people have a tendency to respond affirmatively to English even if they didn't understand it at all. They'd simply nod and smile, which makes for a polite conversation, but no actual understanding or resolution of the problem at hand. I picked up this annoying habit when I was there, and would do the same when I spoke Japanese, just nodding and smiling rather than questioning people and making them repeat themselves (this is one of the reasons my Japanese really sucks).
The next level of faking languages is to learn a few key phrases/words and string them together in different combinations. Good words are "like", "hate", "this", "that", "man", "woman", your nationality, etc. The first time I came to Korea, my thoughtful friends taught me the Korean words for "like", "hate", "Korean" (person), "Japanese", and "American", and were quite entertained as I proceeded to have the same conversation with everyone about whether they liked or hated the different nationalities.
The level above this involves learning actually useful question words, along with a few declarative phrases. This guy I know in Korea has this down-pat, and actually convinces most people that he speaks and understands Korean, but I'm pretty sure he only knows about 20 words. So, like the Rock, he relies on exaggerated facial expressions, and is clever enough that if anyone asks him for details in Korean, he just responds with another question, a more exaggerated facial expression, or ignores it completely. It's fascinating, because I think people actually think he speaks Korean.
Of course actually learning the language is better than faking it. Yesterday on the subway some Korean guys were talking about me (not sure what they said), and I got them really flustered by telling them that although I'm a 백인 (somewhat derogatory word for white person), I could speak Korean, to which one of them said, "shit, he really can speak Korean". Hah. Watch out, people. I'm onto you.