I agree with Dave that key signatures should not be used with decatonics. They should be reserved for rather special cases of microtonal music, anyway. In the case of decatonics, they certainly make reading the notation slower and prone to mistakes.
In classical music - the most notation-based genre - marking every single note with an accidental has been quite a common practice for hundred years now and educated musicians are used to that. Key signatures are not common even in tonal 20th Century music.
For easily readable notation of contemporary music, performers expect
more accidentals rather than less. For example, natural signs should be used even when the note would be a natural anyway, if it has been chromatically altered in some previous bar. In chromatic music, an accidental should be repeated when a note comes back in a bar, even if the accidental affects the whole bar. Otherwise players will invariably ask which one it should be, and valuable rehearsal time will be lost. If an un-inflected note (say, D) follows an inflected note (D
![sharp :#:](./images/smilies/conventional_sharp.png)
) right after a bar line, it is actually a strict rule in all music publishing houses (if not in music theory books) that the latter note has to be cancelled out with a natural sign (D
![natural :h:](./images/smilies/natural.png)
).
In microtonal music, it's particularly important to use a lot of cautionary accidentals. Key signatures may be useful but it's important to decide case by case whether they make the music easier or more difficult to read.