Generally you can put your plants in the ground after last frost/freeze date for your area. If you grow in containers you can put them out earlier because you can bring them in to avoid temperature dips.
Here is a link you may find helpful.
NCDC: Freeze/Frost Maps
I like to start plants indoors at least a month before I put them outside. A more mature plant can withstand temp extremes better than a little seedling, or a smallish clone. The earlier you put plants out (in ground especially) the bigger the plant gets before it starts to flower....voila...bigger plants, bigger yields.