Does the determiner “some” also describe “milk” in the sentence below? Or it only describes “bread”? I’d like some bread and milk.
Yes, I do believe that it would also describe "milk" there. At least, "I would like some bread and some milk" sounds exactly the same, if not repetitive.
When multiple items are listed, any adjectives generally carry over unless specified else. See this:
I saw a lot of red cars and trucks.
Here, both the cars and the trucks are red, as there is no adjective before "truck." Compare this to:
I saw a lot of red cars and blue trucks.
Here, only the cars are red, as the trucks are described by the adjective "blue."
Thus, in "I would like some bread and milk," "some" carries over to "milk."