What is the character encoding of the data provided by Geo Planet? Is it UTF-8?
Yes; the GeoPlanet documentation says "Yahoo! GeoPlanet is UTF-8 compliant and supports location names for usage variations and in multiple languages, including English, French, German, Italian, Spanish as well as local double-byte character set data in Japanese, Traditional Chinese, and Korean." (http://developer.yahoo.com/geo/geoplanet/guide/concepts.html#language). Additionally, UTF-8 is specified in the response XML (http://developer.yahoo.com/geo/geoplanet/guide/api_docs.html#response_formats)