This sounds like a great one-way cruise.
Acapulco = There will be plenty of taxi cabs at the port either VW beetles or SUV's. There did not seem to be much in between. Try to get someone to go with you and ask for an SUV. Just tell the driver you want a half day tour of Acapulco to include the Cliff Divers, stops at good silver shops like Tasco and go out to the Princess hotel if your driver can get permission for you to walk around the property, it is very pretty. Our cost was $60 per couple (we ended at our hotel for a post cruise stay).
Costa Rica- Punteranas or Limon? At Punteranas, we took the ships tour to the Corobici River for rafting which also included lunch. This is not white water rafting, but a great fun way to explore this country. If you port at Limon, there is a red canopy tent area just as you get off ship with a board of tours & prices, thus no haggling. We took the private #1 rated tour recently to Tortugero Canal and the Banana Plantation @ $45pp. This half day tour was great and included the canal boat tour price with many other photo opportunity stops. The tour of the Dole Banana Plantation was also very inclusive. I will forever appreciate each banana that I eat.
Aruba - another do it yourself island/port. A half day tour is plenty to include a stop at the California Lighthouse, the Natural Bridge, and only if you are interested, a stop at the bat cave and stops at various picturesque areas like Baby Beach. When you return from the tour, take a city bus just across the main street from the pier area to Palm Beach ($2RT). Ask to be let off near the Holiday Inn. This beach is beautiful. If they don't have a convention, they will probably rent chairs to you.
Enjoy the Infinity.
We were on Infinity trans-canal last December (and will repeat this December) from SD to FLL.
We hired a cab in Acapulco (wasn't a VW or SUV - can't remember what it was!) We negotiated half day for $50 (which included tip and divers)). Actually an interesting tour - we asked him to show us what was of interest - and he pretty much did the rest...we were actually with him aboutr 5-1/2 hours in all. Pretty good experience and will probably do it again this time.
In Costa Rica, we did our only excursion - Traditions of Cost Rica. Was interesting.
We are repeating this cruise mainly because of the number of sea days....it's a great cruise on a great ship (will be our 3rd time on Infinity).