I decided to check it out for myself and see what more I could learn. Wiki starts out with, "The Monarch Butterfly is a Milkweed Butterfly..." "They are becoming common in Bermuda due to increased usage of milkweed as an ornamental plant in flower gardens." "Monarch butterflies are poisonous or distasteful to birds and mammals because of the presence of cardiac glycosides that are contained in milkweed consumed by the larva." "Being the sole source of Monarch Butterfly larva, the plant is often used in butterfly gardening."
My only connection to milkweed is that they're just another nuisance weed to farmers and there's nothing nice-looking about them, either. And the milky sap inside is gross. The photos on that I found on the net first looked nothing like what I was used to. These plants were pretty enough that I figured they could not possibly be milkweed.
The above 2 photos are more what I remember milkweed to look like, including the gooey white milk.
Glad there's more choice than just the common milkweed.
It turns out that now's a good time to think about planting milkweed. http://www.butterflyencounters.com/ says to plant in fall because, "Many species of milkweed require cold moist stratification to trigger the seeds to germinate." People with 'Butterfly Gardens' know this already and now that I know, I'll be looking for some sources for seeds.