This is the day when the Saints are remembered and flowers are placed on gravesites all over Costa Rica. It's a beautiful tradition in the Latin American culture.
Halloween isn't really observed here in the American tradition of trick or treating but the Costa Rican children are catching on more and more as the years pass.
I heard of a story where a little girl was dressed in costume and went to a Gringo's house to trick or treat. She announced "Halloween, Halloween" (instead of the usual "trick or treat") and the owner of the house (dressed in a wolf costume) opened the door slowly, hairy hand reaching from behind the door and then he showed himself in full wolf form. The little girl screamed and wet her pants. I guess she wasn't expecting the "trick" part of it all, she just wanted the candy.