Yes, Disney CMs are usually really accommodating. All the same, it's usually nice to mention to them that you are wanting only drinks, or dessert or an appetizer, and if you don't plan on staying as long as you would for a full meal. As a former seater/hostess (non-Disney), it make things a little bit easier to know if someone was going to be done with a table within a general time frame. Sometimes when it's busy, you might even get seated quicker than you think, since they might try and squeeze you in somewhere knowing you won't be long.