Hello, LucasVieites. Inititally my installation and backend were in English and frontend in Russian. Later I tried all-Russian installation but the result was the same in both cases: all messages from the WordPress itself were in that language which I expected them to be (English only at the backend and only when I wanted it to be there) but my Esplanade”s child theme talked to me exclusively in English.
Fortunately I have found a way out at last. I used the Codestyling Localization plugin for translating all the Esplanada’s messages. I had to translate the theme only once and now plan to get rid of the plugin in my WordPress installation. So I highly recommend this plugin to everybody who has problems with Esplanade’s localization.