First sentence

[Vawm tsamsiyu]

How would I say "I don't speak English" so can pretend I don't speak English To people trying to sell me something I don't want or make me do something I don't want to, and confuse them 
here's my wild stab in the dark

  oel ke plltxe 'Ìnglìsìti.

And if they keep talking

pelun nga lu vä

why  you be noisome, unplesant to the senses

that's the closest I could get to "why are you bothering me?"
                 

[NeotrekkerZ]

You're pretty close for the "english" sentence, but you use the adverb in Na'vi:  Oe ke plltxe nì'Ìnglìsì (I don't speak Englishly).  Or you could say Oel ke plltxe lì'fyat le'Ìnglìsì (I don't speak the English language).  Note the endings on "oe" in both examples.

[Muzer]

Your second one sounds right, except you missed the glottal stop off the end of vä'. You can add a "oeru" there somewhere (pronounced weru because of the ending, see Na'vi in a Nutshell for more info) to mean "to me" - why are you annoying to me.

I can't think of a better way to say annoying, however.


(the dative case, the "ru" and "u(r)" endings, turns nouns into the indirect object of the sentence - in English, most (but not all) of the time this corresponds to the word "to" being placed in front of the noun - I give the money to the person, for a simple example).

[kewnya txamew'itan]

Oel ke plltxe lì'fyat le'Ìnglìsì

Whilst in many cases lì'fya solutions are the best way of describing languages, I don't like the transitive use of plltxe here. I'd just stick with the one we know to be correct, the nì- solution.

[omängum fra'uti]

It's possible to use lì'fya here, but not in that sense.  You speak by means of the language, so "fa" works great.

Oe ke plltxe fa lì'fya le'ìnglìsì

[kewnya txamew'itan]

It's possible to use lì'fya here, but not in that sense.  You speak by means of the language, so "fa" works great.

Oe ke plltxe fa lì'fya le'ìnglìsì

I hadn't thought of that, you could indeed. Although I still think that the nì'ìnglìsì way is more elegant (it saves two syllables) 

[Vawm tsamsiyu]

So "Oe ke plltxe nì'Ìnglìsì" would be how I should say I don't speak English if I want to keep it shorter and easier to say?

And "pelun oeru nga Lu vä' "   For why are you bothering me?

[kewnya txamew'itan]

Yes.

[Vawm tsamsiyu]

Irayo