I have done this route three times--once on RCL and twice on Princess.
This is one of my absolute farvorite places to cruise and I really enjoy the ports of call. It can be a little cool when you leave L.A., but it warms up about 1/2 way to Cabo.
In Cabo we like to go sea kayaking out to Los Arco and to Lover's beach. In Puerto Vallarta we have done mountain biking and the canopy tour and enjoyed both. There is also a wonderful boardwalk along the ocean in the center of town. In Mazatalan we enjoyed the Sierra Madre tour which took us to Concordia and Copala. This tour allowed us to get out of the cities and see the countryside and small towns.
You will have a wonderful time.