Yup. But only for sites that have yet to be created.
Say your My Sites Web Application is hosted at http://my/
add /_layouts/regionalsetng.aspx to the URL so it's http://my/_layouts/regionalsetng.aspx
then configure the settings you want. each new my site created will now pick up those settings.
BUT this has to be done before sites are created!!!
you *cannot* recursively do this for existing sites through the Admin UI - you'd need to code a utility to "fix" existing sites.
Cheers
Spence
www.harbar.net