Advanced Language Selector is a very simple addon that allows you to play ESO with English texts but another language's sound files/voices.

To do so, after downloading this AddOn, simply start your ESO launcher, choose the language you want the voices to be in and let it update (this is only necessary if you played in English before).

In case you used to play in another language than English and you're having any problems with this addon you will need to let the launcher download the english textfiles by setting the language in it to "English".
Afterwards you can reassign your chosen language.

That's about it. The initial loading of your character will take longer than usual because the texts can't be changed before character selection, however you won't notice any performance issues/longer loading screens afterwards.