yes, they are compatible.
But, it depends on the size of your tank and the size of the angels and discus.
I don't know if I'm completely right, but the angels must not be biggers than the discus you already have.
Someone correct me if I'm wrong, but I think its b/c the angels are faster than the discus, and being territorial fishes too, they could not let your discus eat well.
Hope it might be of some help