Lying in English - I was with a friend...

There are many ways in which you can exploit the fact of not being a native speaker when someone asks you a question you don't really want to answer to. I find particularly interesting like in English you can actually avoid saying if you spend the evening with a guy or a girl, just saying that you were with "a friend". In Italian you can't hide the sex of your mysterious friend... it would be "un amico" or "una amica" - and it makes a big difference. I've heard that in Japanese you also have the same word for single and plural and so the description of your evening would be even more vague, not being able to distinguish between a date and an evening with a bunch of guys. Can any Japanese speaker confirm that?
And do you exploit not being a native speaker? I'm sure you do!