I use spinach instead of lettuce too. I'm crazy about spinach. I chop it up and put it in everything!
I've been taking salads to work for lunch. I boil a bunch of eggs and the night before I throw a chicken breast in the oven. So I have protein. Then tomatoes a little cheese and Some dressing. I load my bowl full! :) you could (on a day off) make 2-3 meals and package them separately so you can grab and warm up.