Shouldn't there be niqqud to indicate the article here? We get it for other ambiguous words, so why not here?
Sure but רוצה is always marked whether you can listen to it or not for example. At least it should play by default it is ambiguous.
also, "we aren't returning to a restaurant" just sounds wrong, so you can resolve the ambiguity through the context
How do you determine that it is "the" restaurant, rather than "a" restaurant in this sentence?
With the audio. You hear LaMisada, not LeMisada. As long as I know, if you have no audio, you have to guess from context.
Please don't use all caps, it's considered rude. The reason is because of "will." That's in the future. This is the word and skill for present tense. In the present you are (or are not) doing something. In the future you will (or will not/won't) do it.
Future: I will drink. Past: I have drunk. Present: I am drinking.