It is my understanding that the restaurants at CS and many in the Epcot World Showcase are not owned by Disney, and they decided not to participate in the dining plan. Perhaps this will change in the future, but the official list does not include them.
That being said, I did read a review from someone who went in January and they were able to use the dining plan at Coronado Springs during their stay.
I would suggest that you call the resort directly and ask. Or perhaps WDW Dining could confirm it.
Of course, you might also watch for reviews when people return to see if they say they were able to use it there or not.
I did write a detailed email to WDW guest services explaining my disappointment over some of the Epcot restaurants not being included, and also stated that if I were a guest at CS, it would be disappointing to not be able to use the dining plan there.
Hope this helps!