Jazz is by far the most complex style when it comes to improvising. Your question has a complex answer:

Jazz cats uses ALL the scales, depending on the context that the chords and/or harmony imply.
They tend to rely on arpeggios, to target the notes that are important in the progression, and they use a tension/release pattern that implies notes that are NOT in any scale/arpeggios that the harmony suggests...
That means that any time, you might play ANY note in a jazz tune, as long as it comes and goes somewhere. My answer is stupid, but it is exact :)
Learn tunes, Jamie Abersold has a list of them (so what, summertime etc...) and play them, over and over.