How Do I Use OS X Dictation While Offline?
Yes, you can use Dictation while offline in OS X Mavericks. Launch your System Preferences (you can find it in the Apple menu at the top right of your screen) and then click on the Dictation & Speech preference pane. Click on the Dictation tab, make sure Dictation is turned on, then select the "Use Enhanced Dictation" option. You need to be connected to the internet when first enabling this option because there is a download required.