The Krystal does allow cruisers to use their hotel facilities for the day. Also the Hotel Molina de Agua allows cruisers to use their facilities on a day use basis.
Molina de Agua charges 100 pesos for Adults, which is around nine dollars. I remember that it is 50 pesos or about $4.50 for children. This is an older Greek-owned hotel that has a lot of true Mexican charm. There are two very nice pools. One is on the beach and the other is on their frontage street, Vallarta Blvd.
The advantage of the Krystal is that it is right by the cruise ship terminal. The advantage of the Molina de Agua is that it is near most of the better restaurants and also near to excellent downtown shopping, if that is your preference.
My favorite lunch places are :
Mariscos Polo for outstanding seafood at a very moderate price.
River Cafe for American and Mexican dishes
Le Bistro for Mexican food with a French flair
El Torito for an excellent sports bar w/ great ribs and steamed shrimp
Las Carmelitas for super meat dishes and by far the most amazing view anywhere in Vallarta
El Adobe for Euro/Mexican faire