If you´re 100% certain you´ll be able to officially establish residency in a month, then I think you´ll be fine putting it down now. By the time your application is seriously being reviewed you´ll likely have your residency, and definitely so by the time you´re interviewed.
Also, by the time you´ll actually need to use your residency for anything official with the state or feds, you´ll have your residency as well, so with just your application in consideration, I don´t see it as some kind of evil/illegal circumvention to get benefits or something presently while you´re actually not a resident yet.