Usually cool on deck the first day at sea from SD. Once down baja you will be amazed at how blue the water is in Cabo, be sure to take a boat ride out to Los Arcos. Take a local one off the pier, less expensive than the ship. Snorkelling is great out by lovers beach.
Mazatallan is a bit seedy but a local cab will get you to the Golden zone beaches and some sight seeing.
In Puerto Vallarta get city tour from the pier taking in the jungle scenery as you go inland.Hot and tropical with breath taking views.
Be sure to see the cliff divers in Acapulco, its about a 15 minute walk from the ship. Be wary of the taxi drivers there, they over charge.