From Bistro de Paris, which is on the second floor of the France Pavilion, you can see most of Illuminations IF you have a window seat. We ate there and the people at the window tables had a lovely view (needless to say, we did not and were sad about it!). This was 3 years ago, and the trees do grow, so I don't know if that would affect the view at all now. Chef de France, which is downstairs at the France Pavilion, is usually blocked by people and trees so you can't really see much.
As for Mexico, it's the counter service restaurant -- Cantina de San Angel -- where you can see Illuminations. San Angel Inn -- the sitdown restaurant -- is indoors and you can't see anything from there.
And yes, Rose and Crown does have the best view, IF you can get a table on the water.
Japan's Mitsukoshi restaurant lounge may have a view -- they have a deck that goes all the way around the building over the store, but I don't remember if there are windows for the lounge, which is on the lagoon end of the building.
And we've probably been sitting right next to kkmauch and not even known it! We usually eat dinner around 6 p.m., then wander the countries looking for dessert (Rice Cream from Norway -- YUMMY!) and sit on the fountain of the isola at Italy to watch the fireworks.