I think the book says you can use any salad dressing that has less than 3 grams of sugar per 2 tbsp serving (I think), but you have to be careful of Caesar dressing because, while it may not contain sugar it certainly has a lot of fat in it.
On SB we watch our fat intake too. Here is a link to the updated food list - it doesn't specifically mention Caesar dressing though.
I would have the caesar salad but maybe ask if they can bring the dressing on the side so that way you can put as much as you need on it - I know a lot of places put way too much dressing on caesar salads. What about a simple tossed salad? It will have more veggies and again you can ask for the dressing on the side - a simple vinagrette would be best. I would also suggest getting a veggie soup to go with your salad - that way you get in more veggies.
Best of luck and don't stress over one meal - if you over do it a bit - just get right back on track afterward. Life isn't perfect.