There are a variety of ways round this. If you want it server-wide go to xsp.properties in <Domino>\data\properties folder on your server. Just uncomment the line for djConfig, and add the parameters you want, as on the Dojo website. I'm not sure if doing a Restart Task HTTP will be enough, I guess it should be. That will definitely work on 8.5.2.
At an application level, you also have an xsp.properties file, available under WebContent\WEB-INF in Package Explorer view. The parameter will be the same as in the xsp.properties, xsp.client.script.dojo.djConfig. When preparing for my session on Dojo at LS11, this did not work for changing the Dojo version on 8.5.2 - the server overrides. But it may work for just changing the locale. It looks like it would work with 8.5.3, because in the beta (may change for Gold) you can change the Dojo version at app level using xsp.properties.