This is a simple but effective improvisation using the same ingredients as I used over the 'Soloing Over Bossa Chords' lesson - scales and pentatonics.

I like using pentatonics personally. They open up the sound quickly and are easier on the ear than a constant stream of scale-based eighth notes. If any of the instructions are confusing see my 'Jazzing Minor Pentatonics' lesson.

Cmaj7 - the first two notes are taken from the Bm pentatonic. Bear in mind this song is in G and we're starting on the IV chord. I'm using Bm pentatonic because it gives a Lydian feel to the chord. The next bar is from the Em pentatonic, in keeping with the key we're in.

Cm7/F7 - this is a Gm pentatonic. It gives a different feel than the Cm which might have been the obvious choice. It comes from realising these two chords are the 2-5 in the key of Bb and one can play either Gm or Dm over a 2-5-1 sequence in Bb.
Gma7 - over these two bars just the Em pentatonic.
Bbm7/Eb7 - same trick as above, using Fm pentatonic this time.

Am7-D7-Gmaj7-Em7-A7-Am7/D7 - the Em pentatonic is used over all these chords because they're all in G. Again, it's the same trick as for the Cm7/F7 and Bbm/Eb7. When it comes to the A7 I included a bit of the G scale to break it up a bit - but not much!

Dm7/G7 - the G altered scale (Ab melodic minor) to introduce the Cmaj7 coming up.

Bear in mind all this is very tiresome to read but easy to play!