Yeah, I can’t help but laugh when other people do, even if I have no idea what they’re saying. But that’s kind of cool if you think about it.
I couldn’t find a link to it, but a few years ago, there was a story in the news from Canada, in which a woman reported that her house had been burglarized. Detectives came to take a statement, and while they were there, the woman’s phone rang. She spoke to her father, in French, about how the police believed her insurance scam, and soon she’d have enough money to buy all new stuff.
When she hung up, one detective said, “Merci!” and however you say “You’re under arrest” in French.
I mean, she lived in Canada. Many Canadians are bilingual!
I was new to this area <still am, since I didn’t grow up here> and absolutely everybody knows both spanish and english. I know english, not enough spanish to matter. I worked in an atmospher of all women, all types, but many, or most, of them very very chatty, gossipy, and often quite bitchy. So when I first arrived I got a LOT of snark in spanish around me. I could understand some of it, and others would tell me when I asked what ‘blah blah’ meant.
Since I was never going to learn enough spanish to really keep up, I decided to play dumb. Which isn’t hard, since I am. But…I played like I was PLAYING dumb. I’d drop in comments in english at times when I could understand what they were saying, and smirk or snort or laugh and walk away other times.
3 years later, most people there truly believe I know Spanish and am just pretending I don’t. 
I remember being on a bus in Glendale, California and hearing a fuss between a Chicano man and another person, when a Spanish speaking lady remarked to me that “Anglos always seem to think we are taking about them if they do not understand Spanish.”
Since then I have seen and heard many examples of this being the case. One time I heard two Mexican men discussing their work in Spanish, when an Anglo man came unglued at them for commenting on a scantily dressed woman he was with.
In Vancouver, I used to listen to the Chinese teenagers gossiping about boyfriends and such, after they had checked that I was not Chinese, so obviously didn’t speak their language. Of course they were right, but I’d wait for them to giggle especially well over something, then burst into laughter and look back amusedly at them as I headed for the door.