Maybe one my butterflies flew from Florida up to you and thought the Plumeria reminded it of my garden.
Just kidding! I have Plumeria in my garden and never seen them interested in it. Plumeria is a deciduous tree/shrub and not related to the milkweed. I believe the sap is poisonous too. They can get big!! Down in the Florida Keys there was one that towered over the second floor of a hotel. Unfortunately a hurricane took it down.
This is just my opinion here...but I don't think that your hatching eggs will grow on Pulmeria so you may want to get them on to a milkweed leaf very soon after hatching. I'm not too sure how you will do that...maybe place some milkweed leaves strategically near the eggs. Seondly, I've never heard that cats must eat the same species of milkweed that they emerged on. Maybe someone else on the forum has that information.