The only restaurant where you will be able to watch IllumiNations regardless of where you are seated is Rose & Crown. They have a reserved viewing area to the left of the restaurant for guests that are seated at tables without a view. Most reports indicate they will not take requests for patio tables, so it'll be luck of the draw.
La Hacienda is another popular venue to try for IllumiNations viewing, but very few tables actually have an excellent view. Some have an okay view and some have no view at all. If you are seated at a table without a view, there is no viewing area to go. I've heard mixed reports about whether of not they'll let you request a window table or not. (If you do request, make sure you request one that has a view of IllumiNations. Some window tables face the wrong way.)
I've read reports that Tokyo Dining has a few tables with an excellent view, but again, no guarantee you'll get one. The restaurants in France (Chefs and Monsieur Paul)a re sometimes mentioned as having a few tables with obstructed views. I've been inside Monsieur Paul while IllumiNations was showing and the view is very obstructed and only a handful of tables have any type of view.