proverb
 

what is the more correct writing of see no evil, hear no evil, speak no evil?
is it 見ざる聞かざる言わざる or 見猿聞か猿言わ猿? or should there be any commas?

also is the reading みざるきかざるいわざる (mizaru, kikazaru, iwazaru)?

I would say that this is probably more a matter of aethsetics than of correctness. You will see both.

I personally never have written and would never ever write it with 猿, but that's just me. The reason for this is that I find it "too much" and "too trying" to use the kanji 猿=monkey in the conjugated part of the verb 見る. To me, it looks too tacky. All conjugations MUST be done using kana is my family precept. Then again, one could just laugh this off saying that it only shows how flexible and playable our language is.

As to your last question, yes it is.