Here are some tips to help you localize your forms. For this, you will need to configure FormBuilder. Using PEAR::setStaticProperty() / DataObject.ini is the simplest way. Unfortunately, AFAIK some QuickForm variables aren't available (e.g. requiredNote). Maybe passing an array to create would help, but I didn't experiment.
The following options can be used in a french UI:
[DB_DataObject_FormBuilder] dateFieldLanguage = fr dateElementFormat = d M y timeElementFormat = H:i:s dateTimeElementFormat = d M y H:i:s linkNewValueText = Nouveau submitText = Envoyer requiredRuleMessage = %s : Une valeur doit être fournie. ruleViolationMessage = %s: La valeur fournie n'est pas valide.