It would be training anyway. 
In public?!?! I say good sirs have some sense of decensy!
But yes, just don’t by anyone and you be good.
-haru
I once was throwing in the street and to my slight surprise not getting much attention (new Yorkers… They have seen it all) when a guy stops his cab very suddenly, and just as I pull off a long string of Eli hops of several types in a combo, he just shouts “YO! Good kid! You… Are… GOOOOOOOOOD!” I was laughing my head off for about five minutes after, still throwing.
I’ve never yo-yo’d in public. Mostly because I’m afraid of accidently hitting someone and getting sued or known as the guy who injures people with a toy. If you’re in a place where people aren’t crossing your path every few seconds I think its Ok. Just make sure you have a new string and in a place where if the yo-yo went flying it won’t hit anyone or anything but the ground.