With lettuces, just try some, because it will just depend on how much light, and we can't judge. You might try some in a container. I use some of those plastic bowl-shaped planters with large surface area.

One approach is to plant more spicy things that add bang for buck, instead of trying to produce a large mass. That way, your crop might be a bit leggy and sparse, but still flavorful. So, try arugula or red mustard, small amounts of which can be added to purchased lettuce (like romaine) and make a great salad and still let you feel like you grew something. Also think of cooler weather herbs like cilantro and parsley that tolerate some shade.

BTW, if you use such containers, you can move them to sunnier areas, if available. Also try to start your lettuce earlier to get some good growth before the shady season sets in--this can also work with containers, to let the seedlings beef up a bit, even if you don't want to keep the container in that place permanently, and then move it to the shadier area. I always start too late, August seems so hot, then fall sets in for real, sun is low and I have similar problems.

Thanks so much for the response! I tried growing a lettuce mix and, while growing pretty loose, got me a good crop!

As for the containers, I'm already growing it in em. Sometimes a pocket of sun peeps through the trees for a whole hour, and I move it in =D