Can anyone tell me if plumeria's are toxic to animals?
I would say yes although there are some insects that feed on other plants in the same family.
If you have a dog or cat that might be inclined to eat your houseplants, make sure to have plenty of 'catgrass' or sprouted wheatgrass on hand, especially if they can't go outdoors.
From what I've been able to find about plumerias it is the white milky sap which is poisonous. I found this about them: Just a word of caution - "Plumeria" belongs to the Dogbane Family (Apocynaceae) which contains other poisonous plants such as Nerium or Oleander. The fleshy branches of frangipani ooze a poisonous milky sap when cut and the leaves of oleanders are highly poisonous.
So I would keep my pets away from them if they tend to chew on plants.