folen,
According to your question on changing data in design mode for a specific culture without effecting other cultures, I would like to provide you the suggestions as follows:
1. Please try to set the Localizable attribute to False so that the designer generates the correct portion of code in the container's InitializeComponents() and not in the resource file.
2. Please provide the related information such as code snippet or the object you use to change the English's design on your project multi-language support implementation in Visual Studio.
The resource (.resx) file that holds the physical attributes of your design surface is a different concept from the.resx files you might add for internationalization. Typically those are used for things like storing text and images specific to particular countries/regions to be used for captions and other text or visual cues that may change depending upon the nationality or preferred language/culture of the user.
3. If you are developing in VB 2005, I would like to recommend you to use My.Application.ChangeCulture method to change the culture used by the current thread for string manipulation and for string formatting. There is KB article on the issue:
How to set culture information programmatically in a Windows-based application by using Visual Basic 2005
4. Additionally, the following article can provide you more information on Resources and Localization:
http://msdn.microsoft.com/msdnmag/issues/06/05/BasicInstincts/default.aspx
Hope that can help you.