Do you mean the text language? Change the language in the paragraph style?
User Interface? Install it in the Czech language.
I have got problem with Hyphenate. (not with using)
There is not support of Czech typohraphy rules.
And some people says, swithing Mac OS Maveerick to Czech, and Indesign to the Czech should be reason for correct Hyphenate.
There are some plug-ins, but doesn't works
For Czech language i have to uninstall Indesign and install again. Now it's in Czech. OK.
But. So, it's my big disappointment.
I use Indesign with Czech paragraphs, my Mac OS and Indesign work in Czech language, and...
Hyphenate doesn't work well. In call-center they sad me, it's not their effort, and i maybe shoud try Plug-ins.
But Plug-ins doesn't work with Indesign CC.
I'm angry, Czech support is suck.