Language is a barrier that we all face when traveling or sometimes when we live in a big city. Many games use a "common" language to remove the barrier and make it easy for a party to interact. I leave it to the dm to decide if a common language exist or not.
Nearly all races should have their own languages and like races may share a language, but with different dialects and regional influences, like American English and British English. Keep in mind that even a persons native language does not grant you mastery over it. Mastery of any language is studied skill and in this system will require points to be added so you can handle yourself properly and not sound like you are uneducated. Sadly to "turn off" your language level if the need arises you need to make bluff check. As a game construct, either you know a langauge or you do not. If there is some similarity to a known language that may make it possible for you to understand enough to communicate. Below is a basic skill difficulty for languages:
- Racial Language: Fair
- Racial Language different dialect: Moderate
- Known Language: Moderate
- Know Language different dialect: Difficult
- Unknown Language, but a familar physical form and social structure: Hard
- Completely Alien: Insane
The above skill difficulties are for your level of langauage. Everyone is considered to have 1 level in their own language.
For every level of read/write language will lower the difficulty by 2 points, so fair at 15 becomes 13 with one level, 11 with 2 and so on.
Failure may still grant you some information, whose in charge, if they seam fearfull of you, etc...