To be honest, when I am in doubt I go with a steak!!! And pick vegetable sides or just ask them to leave out things like mashed potatoes (but you already suggested this). I don't know if this is your thing, but if you're worried about salads, try soups as well
So much harder to over eat on soups, especially if it isn't cream based. Maybe not as filling though but as a substituted side its great for different flavours and to keep you from getting sick of chicken salad everywhere you go. My other suggestion is ask. Ask and ask and ask! Don't be afraid, even if the answer is no, no one is going to refuse a politely phrased question. Say "hey, can I get that without the dressing?" Or "Hey, can I get this burger with the sauces on the side?" "Can I get this without cheese?" Some burgers can be pretty good if you strip them down... Take away the bacon but keep the veggies and the tomatoes, etc. You might be able to fix up a lot of the "less" stellar options to be real winners!
And, assuming you eat multiple times a day on a trip maybe you can try and make something last lunch and dinner at restaurants. Order a pasta but ask for a to-go container right away. Before you even eat split the meal in half, saving the rest for later in the doggy bag. Its not on the plate anymore and harder to eat. Remember that veggie based sauces are better than cheese and cream, etc.
And drink water!!! Or tea!!! Stay away from in the sodas and juices. Hope all goes well and others who are experienced in travel chime in with great tips and advicd.