Translate, all japanese I know

Hello, I am about to travel to Japan to study Japanese, for the moment my Japanese is very limited to specific phrases.
I'd like to know how to say "that's all the japanese that i know".
I'm thinking it could be both a usefull sentence to explin my situation and a funny joke, like for instance:
-Watashi wa jagaimo desu.
-Kore wa pen desu.
-[that's all the japanese that i know]
Commence laughing.

So, how do you say it? I'd like to have it in Hiragana aswell as romanji thank you.

Watashi ga shitteiru Nihongo wa kore de zenbu desu.
わたし　が　しっている　にほんご　は　これ　で　ぜんぶ　です。

You could start by saying ,

Nihongo ga sukoshi hanashimasu....

(I speak a little japanese........)
Then your one line ......
Then "Sorede zenbudesu"
(Thats all).....

Commence laughter

Thanks alot! Those were really great awnsers! Appreciate it. :)