It may not be too late to plant, but:
While planning your plot, take a few hours and read the posts on this site. You' ll find almost all the answers to your questions.
When you have read these posts, try this site for more info. (I copied this site from farmhunter' s post.)
http://www.qdma.com/articles/list.asp?CAT=FOOD

When you have soaked up all of this info, you will have a better chance to make a successfull plot.

This is the first thing a lot of these fellows will tell you. Get a soil test!
Russ