That there is nothing outside the text for Derrida simply means that the language as metaphor goes all the way down (arche-writing). This is not to deny reference in language as Derrida himself protests:
It is totally false to suggest that deconstruction is a suspension of reference. Deconstruction is always deeply concerned with the 'other' of language. I never cease to be surprised by critics who see my work as a declaration that there is nothing beyond language; it is, in fact, saying the exact opposite. The critique of logocentrism is above all else the search for the 'other' and the 'other of language'.
Derrida in suggesting that a context can never be completely fixed or stabilized, is really only saying that contexts overflow, that contexts are always in a state of flux, and as finite beings we can never hope to 'master' a given context. Thus a context is never 'complete' there is no total context. (This is not that radical of an idea, considering the fact that anyone doing serious historical study understands that history is a discipline of revision.) The problem, or the radicalization, of Derrida enters when we assume that because contexts are always and already under-determined that it naturally follows that all contexts are indeterminate. In fact, surprising to some, Derrida places a large emphasis upon reference, context, and community in interpretation. What Derrida is opposed to then, is not the impossibility of interpretation or the determination of communities as such, but rather the determination of communities under the naive assumption that no determination has taken place - that interpretation follows a set of 'natural' or 'self- evident' rules. These rules usually contain, as there chief means of determination, the notion of authorial intention. For Derrida the author's intent is not something that is 'perspicuous', it is not to be simply read off of the lines of a text. The derridian notion of the 'author's intention' is not some magical hermeneutic elixir which escapes the conditioning of contextually; but neither is it a chimera.