It works very well, just do it.
Some people will notice before others, but that's fine. It's kind of fun watching as people figure it out one by one. I did a table hopping gig a little bit ago, did this for a table of four. Two parents, two kids. It was funny watching first the mom, then the dad, then the daughter then the son (Who I was focusing the trick on) finally figure out that the card was in my mouth.
When I do it, since it's part of my ACR, I snap my fingers over the deck and pause for a beat or two, then point up. Usually what happens is people stare at the deck for a second, then my finger, look confused, then look up and react.