relaxing on secluded beaches and getting away from tourist spots
Sounds like a great cruise! In Acapulco do the cliff diving. It is quite near the port of Acapulco and there ae also some great beaches within walking distance of the ship.
For isolated beaches, in Puerto Vallarta visit El Anclote Beach at Punta Mita. Great palapa restaurants, but for some of the most beautiful beaches in the world, walk to the left facing the ocean and you will find deserted beaches that are to die for. After 45 miutes or so you will hit the surf spot known as "La Lancha". Hike up the steps over rock promenade into a wonderful cove with many more after it. It is the epitome of a "secluded paradise".
In Ixtapa, go north to the surf spot known as Saladita or to Kandhar or Trocones beaches. Once again, you will be treated to deserted paradise.
In Cabo, there is a great beach known as Zippers right before hitting San Jose Del Cabo, some 18 or so miles from Cabo San Lucas. It is also a great surf spot.
I hope this is what you are looking for.