Reminds me of when I used to work in Tokyo, we'd go out for beers after work. If it was just the two of us, we would ask for "futatsu bieru" which may or may not have meant "two beers". If there were four of us, we'd just ask for "futatsu futatsu bieru" and hold up four fingers.
I wasn't nearly as bad as the Aussie guy who'd been there a few years already. We walked into a restaurant once and they all shouted "irashimase" (welcome). Even I knew what that meant, but he turned to me and said "What ARE they saying?". He simply never bothered to find out.
I learnt "mushi-mushi", essential when picking up the phone!
The strange thing about that was that they knew, at once, that I was a foreigner and switched to English. I thought that I could say it like a local !