I find this topic absolutely fascinating and exciting. I think in-game 'race' languages are a huge boost to RP and add a lot of depth and immersion.
As some are already aware, I have been an avid student of Arka's Stonebreaker language for about 11 months now and even chose a Pel Perrakithor name for the guild that was handed down to me. My character and I have both been learning the language at the same pace. From my character's perspective, he grew up with parents that basically sold their wares to the general public and spoke only the normal 'common tongue'. Combined with the fact that Arka's Stonebreaker was almost 'lost to history', he was never exposed to it until after meeting Arka and learning of her research. So, learning it now is his way of 'getting in touch with his roots' so to speak. Although my guild may have a Stonebreaker name, one of the main beliefs of it is that there is something worthy about all races and their cultures (including their
languages). While my character is very proud of his Stonebreaker heritage (and language, of course), he is very interested and open to the cultures, beliefs and languages of other races as well (as am I as a player). We are both very interested in learning more about the Enki language that Darkmoon is working so hard to develop. Cheers to Darkmoon.

I don't see in-game languages as a way of excluding players or characters, but rather as a tool for immersing myself deeper into RP. If I use Stonebreaker, I am always willing to translate if someone does not understand. I am not sure if Peacer's OOC translation is the best way solution, tho. Although technically the player would understand, our character still may not understand what was said. I will often just state something in Stonebreaker with the translation right after (both IC). It makes sense to me that way because not only is my character reinforcing what he is learning by stating it in both languages, he is also being considerate to other characters who may not speak it or speak it well. Furthermore, I see it as a possibility that when learning a new language, you may just say something in that language without realizing it. So, along that line, I will occasionally purposely throw out a Stonebreaker phrase (usually when with others that I RP with frequently). Often this provokes a 'Pardon me?' type of response to which my character will respond with 'Oh. Sorry. <translation>.'
While everyone might not have the time, will, or ambition to learn even one race language completely, most can probably pick up on a few basic greetings such as 'Hello' and 'How are you?' fairly easily. And for those that have the desire to learn and incorporate it into their characters, they can enjoy it, share it with others and provide a translation. So, I see no harm in that.