Watch the Available Scales online guitar lesson by Larry Carlton from 335 Improv
There's a great deal to learn about note choices from scales even if you don't use a scale-based approach in your improvisations. And as I've said previously, you certainly do need to know your scales. So let's look at four scales that will work well over each of the chords in our I-vi-ii-V progression:
Dbmaj7 (I chord) - use Db major scale
Bb7+5/b9 (vi) - use B melodic minor
Ebmin7 (ii) - use Eb minor scale
Ab13b9 - use Ab diminished
Again, even if you don't rely heavily on scales while soloing, each scale represents a palette of notes that will work over the chord in question. They're also valuable for linking chord changes together, which we know by now is the meat-and-potatoes of a good improvisation.