If it helps, here are some key/interesting bits from 'Languages in Traveller' (JTAS 16, pp.28-33 by Terry McInnes):

Galanglic - a dialect of Anglic - official language of the Imperium

widely spoken as a first language only by the general population of major worlds on comms and trade routes
spoken to a lesser degree on other worlds as a second language - their first language will be a different anglic dialect or a totally foreign language (your Hittite, presumably!)

- the more isolated a given world is from trade/comms routes, the more difficult it will be for a visiting adventurer to understand the planet's dominant language

- balkanized worlds may have more than one language

the article goes on to give rules for modifying NPC reaction tables to reflect all this.  Essentially characters can suffer a language ignorance penalty of from 0 to -3 on the encounter die roll - influenced by tech level, starport class and being on an x-boat route or not.

-1 is said to be the difference between US and UK English

-2 "a Texan speaking with a Liverpudlian or a Georgia hillbilly speaking with a native of India"

-3 "virtually a different language e.g. Spanish vs Italian"

There are some specifics on aliens always being at -3 DM and then an interesting bit on naval characters:

"naval commanders or ship captains lost their fleet or ship tactic skill levels if they are commanding a fleet or ship with a foreign-speaking crew.  The language DM for the crew's native world should be subtracted from the 'to hit' rolls made on gunnery tables to reflect the disruption in the chain of command caused by language problems."

which rather goes against our agreement that large IN ships would have lots of interpretation skills!

On the other hand, my assertion that traders would gain an advantage by learning the local lingo is supported in the next paragraph with a +1 DM when rolling for resale on the speculation table in Book 2 if they "have acquired skill in a world's foreign language".

There are then exceptions to the penalty DM in starports, for merchants with more than three terms, or for balkanized worlds which are more complex.

Back to the situation under discussion, certain skills give an advantage:

liaison - "which reflects prior language training"

streetwise - "... includes the ability to quickly pick up a rudimentary knowledge of the local language and imitate the local accent to as to more easily get along and blend in..."

broker -

trader -

    (both these last from _Merchant Prince_ special supplement but no note of how they affect language)

Then there are rules for learning languages (hour/day with tutor + hour/day study: rudimentary knowledge in 6 months; a year of that you're fluent on a 6+ roll on 2D).  Living in the language: working knowledge in 3 months and automatically fluent within a year).  INT 9+ can reduce those times by 25%.  Language teaching computer programs available - but expensive! (can replace tutor)

Some other notes:

Galanglic - based on English but has absorbed words from French, German, Russian, Spanish, Japanese, Mandarin and Vilani

Members of the Imperial armed forces are required to speak Galanglic in addition to their native dialect or language

Galanglic official language of Solomani Confederation BUT

many Solomani settled worlds have Terran descended languages such as Hispanic, Germanic, Slavic, Hindi, Hamitic and Sino-tibetan in addition to various other tongues carried to the stars by the great waves of emigration from Earth during the Rule of Man (often to preserve native cultures and languages)

other variants of Galanglic in Sword Worlds and Darrian Confederation

other examples given are of Finnish, Arabic, German, French and Mandarin variants

Vilani has High Vilani and local Vilani based dialects

There's a Language DM Matrix cross referencing tech level with starport type.

I think if you throw in the dozens and dozens of minor races, it's safe to say there are hundreds if not thousands of languages in Known Space.  :-)

And given that, I would suggest it's not much of a stretch to think that skilled linguists are common despite language translation software.  (Although I appreciate this may depend on your view of Artificial Intelligence in Your Traveller Universe.  e.g. Look at Google Translate now.  Pretty brilliant as far as I'm concerned on, say, German or Swedish (although it still fails at more 'literate' language and idiomatic usage); nearly useless on Japanese. 

Is that the best it will be able to do until stronger AI comes in, or will we eventually be able to communicate easily with any (known) language?  Personally I'm sceptical of the latter happening any time soon and personally prefer a Traveller universe where there's room for human acquisition of language, as per McInnes article, rather than a pure reliance on machines.   See the fun to be had in  _Adventure 4: Into the Unknown_ where it's quite fun to learn a little sign language to throw at the PCs!

I don't disagree, however, that landing on a world with an utterly unknown language, wouldn't present problems.  Particularly if its a true alien language.  (See the wonderful _The Book of Strange New Things_ by Michel Faber for an example of a language that feels really alien.)  But problems are what adventure is about!  With the right group of players this can be a source of a lot of fun/interest - though I can imagine others might run a mile.

I'll finish with McInnes' beginning:
"A word innocently uttered in a tavern conversation triggers a major brawl . . . a merchant suddenly becomes insulted and cancels a profitable trading deal . . . a squad of soldiers fails to open fire at a critical moment and a battle is lost.
These and other disasters can result from misunderstandings caused by dialect and language differences as adventurers journey from world to world and interact with the local populations."

tc