The Palawan butterfly farm is a tourist attraction about 20 minutes outside of Puerto Princessa. It's a large screened in area where cocoons are kept until the butterflies hatch.
From town you can catch a multi-cab for 17 pesos or hire a tricycle and have the driver take you out there and wait till you are ready to leave. For most travelers an hour should be enough time to get a good enough look.
It is easy to get pictures because the butterflies are basically imprisoned but at least the birds can't get at them.
They are supposed to be easier to see in the early mornings before it gets too hot because they will take refuge in the shade.
It was a rainy afternoon when I stopped in so they were still active.
The entry fee is 50 peso.
There is a vantage point (Bakers Hill) with a restaurant across the highway and up the hill a few hundred meters where you could get something to eat or drink while taking in the view before heading over to the crocodile farm or back to town.