With no prior knowledge, very hard indeed. Just press "Yes" to everything, you won't lose out on anything. Try sites like serebii if you get stuck on the puzzles and stuff.
I played threw it without reading anything, except the tourist guy.
It was pretty easy, since the game is made for 3+, and I don't know many three year olds that can read. Then again, I don't know many three year olds. =o