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Google's advice is always to do things with the end user in mind. The search engine wants to act like a person and not like an algorithm. Don't think about "SEO." Think about people. In this context, I would think about the target audience. Would the audience prefer that all of the site's elements be written in the language that they best understand? Of course. So from a user-experience standpoint, I'd highly recommend that everything be translated. Just in case you're not aware of the best practices for multilingual and international SEO, I'll refer you to these resources at Moz, Aleyda Solis, Google and more: https://support.google.com/webmasters/answer/182192 http://moz.com/blog/hreflang-behaviour-insights http://www.internationalseomap.com/ http://moz.com/blog/40-plus-tools-to-advance-your-international-seo-process http://www.aleydasolis.com/en/international-web/successful-development/ http://moz.com/blog/the-international-seo-checklist http://searchengineland.com/the-ultimate-guide-to-multilingual-and-multiregional-seo-157838 Good luck!