I use MailChimp with the MailChimp WordPress Plugin and have configured a List Field and *|MERGE|* Tag for selecting the language.
As "field type" I use "multiple choice".
The multiple choice select buttons are displayed using the native code, but not using MailChimp WordPress Plugin and the according wordpress widget.
In the widget, only a form field instead of multiple choice select buttons is displayed.
Here some screenshots:
widget (with bug): http://twitpic.com/387otu
form (ok): http://twitpic.com/387p2p