Language problems...

Firstly, in response to you Oli.

I agree with you when you say, that language does not undermine Sartre's work in its philosophical validity.
'Thought', can be elaborated in the language used to express it. Here I am taking the Neo-Classic approach that language is the 'dress' of thought. And that such language can be used to express any given thought, but without any intrinsic change by the 'procedures of style'. (The Art of Poetry: Pg 52)

However there is a great power in discourse, in particular as you have said, in the way that Foucault would contend. Discourse is not simply the language used, or the words spoken. But also how this language and these words are received; how they work in a social reception. The validity of a given argument, can further depend on how it is received. How it is discussed or debated, can rest on how 'it' has thus been articulated in the first place.
Most importantly, the meaning that is further extracted can also depend on language, and how this language has been used to convey an idea. (I must point out here that 'meaning' is by no means fixed. Meaning by its very nature fluxes. But with regards to any given philosophical theory, the meaning assigned by the philosopher is crucial to the inter-workings of their theory?)
This is where I think Sartre stumbles. Perhaps he didn't mean to debase women, students, waiters etc. But the ways in which he has articulated his examples, have given rise to such responses, especially from the voices of feminism. Yes, the intrinsic thought does not change. But this thought or idea can be expressed under various guises. The ways in which Sartre chose to articulate his theories, were perhaps not the best therefore. And this is rather a huge failing on his part. Language is essential to the communication of thought. Does the thought exist for any 'other' if it is not either spoken, or written down? The idea, to be taken in the way it was meant to be recieved, thus rests heavily on the form in which it is externalised.
You say Oli, that 'we should be careful no to appropriate meaning to terms because of the commonsense applicability which encapsulates them'. However in various instances the terms used by Sartre are simply nonsensical:
“What must be the being of man if he is to be capable of bad faith?”/ Take the example of a woman... '( Sartre Pg 55). This, is not so much a word game ( as I admit can be taken with your example of the waiter 'playing with his condition'.) This is more a failing of words on the grounds of terminology.
Sartre's theory as a whole however, does not fall down on its expression. But it is important to acknowledge how his choice of wording at times, has led him to such criticism. While this can be seen as 'nit -picking', it is of importance, because Sartre does either one of two things. He either firstly, undermines the validity and power of language by using it so carelessly.
Or secondly, 'writes as if he could speak of the conscious life of those in his stories, by the same right as he projects his own consciousness of a situation'. (Genre and Void. Pg xxvii) If the second, Sartre 'speaks as if for the whole world. (Genre and Void. Pg xxvii)'. It can be argued then, that Sartre not only undermines, but also speaks for others. Whether this is the case or not however, is debateable.