We have been to Cabo on both the Diamond Princess and the Sapphire Princess. You are correct about this being a short stop with very little time in port. Both times we booked shore excursions through the ship for the express purpose of getting off the ship early whithout having to wait in line. The passengers booked on the shore excursions with the early departure times are the first passengers off the ship. I would recommend you do this in Cabo.
We particulary enjoyed the Kayak excursion where you kayak out to Los Arco and spend some time on Lover's Beach. We then had several hours to explore Cabo on our own before returning to the ship.