I thought this was interesting on volunteer efforts to create habitat for migrating monarch butterflies.
Here is my advice. I don't know much about feeding and attracting adult butterflies, but we sure found the recipe to getting caterpillars and cocoons. When I lived in Texas (Houston to be exact), my dad planted all kinds of flowers and herbs around the yard in pots. However, each year, the parsley would be absolutely mobbed by monarch butterfly caterpillars. We soon gave up growing parsley for food and did it just for the butterflies. Every year, cocoons would start showing up all over our parsley, and on one day a year, we would have a massive monarch butterfly hatch.