It's been awhile since I've been up north but you might check out Del's Restaurant in downtown Tucumcari or Joseph's Restaurant in downtown Santa Rosa. Both serve excellent food! In Albuquerque, try the Mule Barn on north 2nd street (don't let the outside discourage you-food and service is excellent!). Have a great trip!
We have eaten at Del's in Tucumcari several times. We stayed at an old Route 66 motel that has been converted into an RV park (nothing fancy, but for $19 per night, it is perfect for an overnight stay) that is about a 1/2 block from the restaurant. Del's has really good, reasonably priced food.