Preheat the oven to 400. Cook the bacon for 12 ish minutes, until crispy. Remove and pat dry.
Cook pasta according to directions. Drain.
While pasta and bacon are cooking, mix the dressing. Chop the veggies too. For the dressing, stir sour cream, mayo, ranch mix, juice from 1/2 lemon, and adjust taste with a litlte salt and pepper.
To a large bowl, add the lettuce, cooked pasta, onions, tomatoes, cheese, chicken, and top with bacon. Before serving add dressing and toss well. If you plan for leftovers, don't add dressing. It will store for a day without dressing.