If planting lettuce transplants, you may have time before they try to go to seed.
Carrots are definitely out of the question.
If you can find onion sets, you'll be able to get enough growth for green onions, but I don't know about bulbs.

It's best to start onion sets in October, then let them overwinter in our area.

EG

Thank you! I was planning to start them all from seed. I suppose I will try the onions (green onions) in the fall, and the rest next Feb.

I believe that most sets are long day onions, so in the south, you would have trouble getting them to bulb up anytime. We mostly have to plant short or intermediate day onions, and I think they are best grown from plants. Here's a good source of both plants and onion information.

http://www.dixondalefarms.com/category/onion_plants

And I think EG is right that getting bulbs for this year might be a longshot, but you could try calling the folks at Dixondale and ask their expert opion if you are really determined. You might could get small bulbs...

PS, I also saw plants being sold at WallyWorld in Atlanta. They had Texas Sweets and Grannex and both of those are short day onions. I think they were like $3.25 for a bunch. So if you have the space to experiment, that may be an option as well.

Here's something that confused me for a while - a set looks like a small dry bulb with no green. A plant looks like a baby green onion - with green leaves attached.

Hope that helps.
Susan

It is too late to plant carrot seeds? I was told I am in zone 7 and told I was in zone 6b. I thought carrots were good all summer! :(

Jengc, I think it depends on where in zone 7 you are. I am also in zone 7 but in NC and we can still plant carrots up until about April 1 at the latest. I think it would also depend on how long is the maturity for your carrots ... mine range from 60 days to 80 days, which would be 3 more weeks into the summer for the 80 day ones. Here, the carrots are done by about June 15. I imagine there are some zones that you can grow carrots all summer, but not here. We can start planting them again about Sep 1 though. Even earlier if we use season extending techniques (such as shade cloths).

They are not going to be very long. I am trying the 6 inch variety because I can't afford another 12 inch box. That soil is expensive! lol so that should cut down on the time too. I tried to grow carrots last year. The tops were BEAUTIFUL! but I pulled them up and there was hardly a root. My daughter wants to plant in the garden, which shocks me because she didn't want to have anything to do with it last year. I would LOVE LOVE LOVE to get some carrots, radishes and lettuce going but I am not going to get my hopes up. Last year, lettuce just didnt like me. If it survived, it took about 2 months or longer to grow to a small size.