So I personally think this is the perfect salad.. around 400 calories.. and packed with protein.
Romaine Lettuce
Black Beans
Fajita veggies
Brown Rice (ask them to go light on the rice)
Tomato Salsa
Guacamole
…
And if you want it spicier … The green salsa only has 15 calories! Plus they have tobacco! YUMM (I like the Milder Jalapeno)
You can find all their nutritional information here as well : http://www.chipotle.com/en-us/menu/nutrition_calculator/nutrition_calculator.aspx