Trish said: I think if I were really on the ball, I could do row covers and actually harvest all year, but I haven't been that good yet.
Oh my, you southerners are so spoiled! up here near the Arctic Circle floating row cover is my best friend (also because the cats tend to dig newly planted stuff up unless it's covered...) I have to think you could easily grow your lettuce throughout the winter, I had some survive in an unheated hoophouse until November or so, and then it grew back early the next year -- (this photo was taken on May 20th)
I bought some fiberglass rods from Gardener's Supply that are very easy to stick into the ground and throw the row cover over. I'm thinking the cover could also be helpful in the hotter weather for you, by helping to hold in some moisture and providing a bit of shade for the plants.
On a slightly different note, nature can be so cruel -- we picked our first asparagus last night, and woke up this morning to about an inch of snow on the ground! oh well, lots of years we're still buried under snow at this point!
