I guess you are asking about changing the UI language of the ReportDesigner. Currently both Telerik Report Designers (for Visual Studio and stand alone) support only English.
In case you would like to localize the ReportViewer you are currently using, it could be easily achieved using the approach described in the documentation: Report Viewer Localization
(that is in case you are using the ASP.NET report viewer; localization articles can be found for each report viewer under Using Telerik Reporting in Applications
, as a subarticle for each platform).
Have you tried the new visualization options in Telerik Reporting Q1 2013? You can get them from your account.