Common milkweed typically requires cold stratification in order to germinate, so if it is cold enough, then a month outside may be helpful. I would question the timing of planting them though--it is quite early for the normal growth cycle of common milkweed. And like Martha indicated, knowing what zone you are in would help very much!

In my experience, milkweed is difficult to transplant, even from a pot. They seem to be very temperamental about having their roots messed with, which is odd since it is sometimes considered a hard plant to get rid of. With the plants from the big box stores, I would just sink the pot into the ground and let the plant reseed itself. Growing from seed, I keep mine in a shaded location every time I pot them up and I try to get to them before they become any kind of root-bound so that I don't disturb their roots while repotting. Right now I have about a dozen each of prairie and whorled milkweeds that I recently potted up from cells to 4" pots. I lost one of those to transplant shock. The next pot-up will be straight into their places in the garden where I will be sure to water daily and also screen (but not block out completely) from much of the sunlight until I'm sure they've taken. A better way to go might be to get the 4" peat pots and sow the seeds directly into those and then drop the pot into place when it's of good size. Once you get a plant or two to go to seed, they will reseed themselves quite happily around your yard and seem to do a far better job than we do.

@beesneedz are your redring plants still growing?

Tropical Milkweed is grown as an annual in your (and my) growing zones. Start some seed inside and once the weather warms up, put it outside and it will take off. Tropical Milkweed (Asclepias curassavica) needs warmth and it will grow well in pots or in ground. If in pots, you can try to bring in before the first fall frost and keep it alive through the winter if you want. Then take cuttings, which will provide larger plants more quickly than growing from seed. Or take your cuttings in the fall before frost hits and pot them up for the following spring. They root quite easily from stems. Mary