Thank god for this, I've been wanting to be able to type using the IME for years in FFXI.
Cool, I'm only a beginner at Japanese and this could be a fun way to practice.
Don't forget the particles, the を particles indicates a direct object. Also, I'm not positive, but I don't think that's the correct word order for 少し, it's a little awkward either way. I would suggest something like たくさん日本語をあまりわかりません. Or a lot of Japanese たくさん日本語 I don't really understand あまりわかりません, or optionally, あまりしりません I don't really know.
If you're going for something a little more positive, ちょっと日本語をわかります. I understand a little Japanese.
The more you know.
I hate to but in here, but the Japanese you're suggesting doesn't sound natural to me.
Referring to the original statement 「日本語少し分かります」, it isn't completely wrong, it is simply missing the particle as Hulan stated. However, わかります does not use the particle を, but rather が, so it would be
"I understand a little Japanese"
If you'd rather say that you don't understand Japanese, something along the lines of:
"I don't understand Japanese very well"
would suffice. Using しりません sounds a little weird as well. Although the meanings of 知ります(しります) and 分かります(わかります） are often confused, the former is closer to "to know" and the latter to "understand". Although explaining further is beyond my ability, here I skimmed a bit and found something that may help.
私は答が分かりません Watashi wa kotae ga wakarimasen = I don't know the answer (literally, I don't understand the answer)
私が答が知りません Watashi wa kotae ga shirimasen = I don't know the answer
But, when refering to people...
私は彼が分かりません Watashi wa kare ga wakarimasen = I don't understand him (As in: I don't know why he is like that)
私は彼が知りません Watashi wa kare ga shirimasen = I don't know him (As in: I've never met him)
When you want to express that you know English, you can say:
私は英語が分かります Watashi wa eigo ga wakarimasu = I understand English (it can also be understood as "I understand and/or speak English"), but some people could think that English is not your native language, you just learned it.
私は英語を話します Watashi wa eigo wo hanashimasu = I speak English
私は英語が話せます Watashi wa eigo ga hanasemasu = I can speak English (literally, I have the ability to speak English), so here people could also think that English is not your native language.
私は英語ができます Watashi wa eigo ga dekimasu = I can speak English (literally, I have the ability to speak English), so here people could also think that English is not your native language.
This one is much more informative but written entirely in Japanese http://homepage3.nifty.com/recipe_okiba/nifongo/027.htm
In a nutshell for the second one:
知ります(しります） having knowledge or knowing something, having information on something, or the experience of something.
「方程式のときかたを知っています」 Houteishiki no tokikata wo ***********
- I know (or have knowledge of) how to solve the equation
「試合の勝敗を知っています」 Shiai no shouhai wo ***********
- I know (or have information about) the outcome of the game
「酒の味を知っていますか」 Sake no aji wo *********** ka
- Do you know (or have experience of) the taste of alcohol?
分かります(わかります） having a comprehension or understanding of a thing, being able to clarify something, or make a judgment of something.
「日本語が分かりますか」 Nihongo ga wakarimasu ka
- Do you know (have a comprehension / understanding of) Japanese?
「辞書を引けば分かります」 Jisho wo hikeba wakarimasu
- If you use a dictionary, you will know (have clarification)
- I don't know (cannot make a judgement) if I will go or not.
Hope that helps some. ^_^