Here in central Florida, I just let the milkweed go to seed, and where it lands, it grows. If it grows where we do not want it, when young, it transplants very easily. I have it in shade, full sun, everywhere. When I have tried to "plant" the seed, it has not grown, or seldom. We enjoy monarchs all over our yard every day, from spring until late fall. (The wasps unfortunately also enjoy collecting the caterpillars, too.) By mid-summer this year, every milkweed stem was just a stick, so many caterpillars were feeding, and the female butterflies were having a hard time finding a leaf on which to lay their eggs!)
I used to release up to 50 or more butterflies per year from tanks set up in school classrooms. Students loved to watch the eggs change to caterpillars, grow, and the whole classroom stopped when they went into chrysalis - or hatched into a butterfly!
I learned that cleanliness counts when raising the caterpillars. Bacteria can harm the developing butterfly, and some are parasitised by certain wasps and flies, and the chrysalis dies. Students learned those lessons, also. One fun memory was when the first newly formed chrysalis greeted the class one morning, and a student asked me if I had painted the golden spots on it!
From one who lives with "weeds", and enjoys butterlies right outside most of the year.