Playing over minor II V I

It's always made the most sense to me to think of the harmonic minor scale as the basic scale for a minor progression like the minor II-V-I, similar to the major scale being used for a major II-V-I. 

The harmonized A harmonic minor scale would contain the following seventh chords: 

I Am/maj7 
II Bm7b5 
III Cmaj7#5 
IV Dmin7 
V E7 
VI Fmaj7 
VII G#dim7 

So, for a typical II V I progression in A minor (Bm7b5 - E7 - Am), you could use A harmonic minor for all three chords to get the basic flavor of the A minor tonality. Though, in common practice, the minor I chord is often played as a minor 7 or a minor 6 (not a minor triad or a min/maj7), if you don't emphasize the natural 7th (G#) over the Am7 chord, it'll sound pretty good. The G# is a half step leading tone into A and kind of naturally wants to resolve there.  If the resolution chord is minor 6, the melodic minor scale works very well for this resolution chord.

Then again, in actual practice, most jazz players will stick different substitute scales over the different chords. Examples include the A natural minor, Dorian, or melodic minor over the Am7; B Locrian natural 2 (6th mode of D melodic minor) over the Bm7b5; and E altered (seventh mode of F melodic minor) or E half whole diminished over the E7 chord.  If the II V I is going by really quickly, especially at a fast tempo, the melodic minor scale from the root of the tonic can be very effective over the whole progression to get the flavor of the tonality.  For an example of this, check out John Coltrane's classic solo over the tune "Mr. P.C." from the Giant Steps album.