This is one of my favorite packet tricks to do, because who doesn't love a good game of 3 Card Monte? Now I've also ran into the same problem that Jerome Hartweg was talking about, and how I used to keep the cards in the black wallet that comes with the instruction book. But then I decided to put the cards into a regular deck, and when I'm ready to perform, I pick up the deck that has the 3 Card Monte cards in it, and go to town.
I've never been called out to ask to see the cards, and the reactions you get with this is simply amazing.
Especially when people say, "Okay, that was cool, but do it again." And since the booklet teaches you 3 routines, you can even ask the spectators after the 2nd viewing, would you like to see it again? And of course they do, and the final reveal will make their jaws drop.
Micheal Skinner's Ultimate 3 Card Monte on Bicycle Cards