I'm pretty sure that soups and salads are considered appetizers. The only possible exception I can think of is if something is listed as serving more than one person, in which case, that many people have to order it together.
This could have changed by now, but my mum and I got the Cobb salad at The Brown Derby. The only stipulation was that since it was listed as serving 2, we had to share it as our appetizer. Your best bet would probably be to ask your waiter/waitress at the restaurant since DDP requirements and exceptions change constantly. HTH