Yes, you'll have to go through the barrister. You'll need someone who speaks that language with you to verify that you have indeed practiced on learning that language and as a somewhat safeguard. IE Ikeelyou the Leuian cannot learn Caneer secretly without at least one thief knowing about it. Of course, you could just easily pull anyone of that race off the street to verify this IC as I've seen it done before, but try not to.

Each race pays different amounts and gets locked out differently (race or class language depending). As an Usil, we pay the least and get locked out the least (one week for a race language, two weeks for class. I know a Human's lock out time for a racial is two weeks. Can't remember how much I paid but I'm thinking 1000 gold for a racial?) No RP interaction is gonna make your lock out time any less, not even if Rafe was bathed in and around Flerians for hundreds of years, it'll still take you the normal Leuian time to learn that language.

As well, everyone from dumb dumb the Oog-ra to smarty the Usil can learn up to 9 languages and this includes Common and your normal class language (which I'm not fond of in either case, but that's the Usil in me speaking). Choose wisely.

The only languages I know that's off limits are the ones you can't find someone to teach you, IE Alarian or Muatana-al. You could learn Arachnian/Monitanian but you can only understand, not speak. RP wise - if someone learned a language that the class/race really don't want you to learn, they may try to harm said character. So Arachnian would tend to be off limits to mages.