In fact I found tow other ways to implement form in widget zone!
First one is to copy form code form MailChamp and put it in text widget!
Second is almost the same but I made one short-code and add labels as attributes. Then I use multilingual text widget witch come with WPML and put shortcut with Bulgarian labels for BG and with English labels for EN. It looks like this:
[mailchamp user_id="FORM_ID_HERE" list_id="LIST_ID_HERE" lebel_txt="Актуални новини по e-mail!" btn_txt="Абонирай ме"]
[mailchamp user_id="FORM_ID_HERE" list_id="LEBEL_ID_HERE" lebel_txt="Subscribe to our Newsletter!" btn_txt="Subscribe"]