+1  A: 

First problem :

The "names values" displayed are taken from the __toString() method result. You could add the "method" options, like this :

new sfWidgetFormDoctrineChoice(array('model' => 'CargoSize', 'expanded' => true, 'multiple' => false, 'method' => 'getName'), array('style' => 'list-style-type: none; display: inline;'))

Second problem :

Your form must embed the i18n form. To do this, put this in the configure method :

$this->embedI18n($cultures);

where $cultures is an array of your cultures codes.

JF Simon
This is funny, the toString I already had. But now after adding the embedI18n, all problems seems to be solved, not only in the sfForm, also in form independet places O_o. So thx a lot for this hint :)
The problem sadly still exsits, I don't know why, but when I want to get the name attribute with: $cargo_size->getName(); // (The values are in the DB for each langugae)It returns an empty string.Do you have more ideas what the problem could be?
A: 

I found the bug. For some reason the culture was set to "de_DE" instead of just "de". With this setting the i18n behavior stuff didn't work!