one guide book says this entrance to the waterfalls not open in early october is that true?

We were there in Oct. 2010, I think around the 9th and all entrances were open.

THANK YOU

Hi Jack. I don't say for sure that things have not changed since then but that is my experience.
You are welcome.

Jack, it shouldn't matter especially if you stay at one of the park hotels (highly recommended). From a park hotel, you simply walk into the park. Plitvice is still worth doing as a day trip but even if one of the entrances isn't open, just park at the other one. They are not that far apart by car. (The whole park is still open anyway.)