Yes, we've used the Dine-Ashore coupons for lunch. This is a great option on N. Majesty cruise as you may find yourself far from the ship at lunchtime, and Bermuda is expensive. You'll still have to pay for drinks, but it's still a very good deal.
You will get a brochure when you board that indicates the restaurants that honor the program, along with their menus and hours. It was easy to carry this with us.
A few things to note. As some mentioned, some restaurants offer a limited menu. So, you need to state upfront that you are with the NCL program. Also, coupons are given only to passengers age 12 and over. And, if you don't use your coupons, return them to the purser's desk for a cabin credit, as the $5 per person charge is made automatically.