As native-english speaker who lived in Germany for a while I would strongly suggest NOT to use geolocation to pick the default language. Use the browser Accept-Language setting to pick the default - this is what it's for and most browsers send it. I can see from the headers on your site that you are using PHP, so here's a link to some PHP code that will parse the browser headers (and correctly interpret their weighting also):

http://www.thefutureoftheweb.com/blog/use-accept-language-he...

You can use this as a starting point to redirect to the appropriate language when none has been explicitly chosen. It's a small touch, but small touches all add up to a nicer experience.