dunno – i agree GREAT language when you don’t want people to understand, though yes you do have to be careful. i have a story about that:
once my aunt (who is completely fluent) went into this cute little vintage store to browse around for five minutes, and while she was browsing, she heard the two men who worked there start saying all these rude things about her in hungarian, like “why does she have to be taking so long?” and “what is she so interested in here already?”
so she stayed in there for almost a half and hour and asked them questions about every little thing.