No, not 꿈 꾸는 사람. That literally means "a person who is dreaming". ^^
A dreamer is either 몽상가 or 공상가. They say 몽상가 is a person who "enjoys" thinking about improbable things and 공상가 a person who always thinks about improbable things.
I am a dreamer. = 나는 몽상가다. / 나는 공상가다.