I cannot speak for black Cubans but seeing no interracial couples indicates to me that without the Cuban revolution things would have been worse for black Cubans.
There were always interracial couples in Cuba. The mulato population in 1953 exceeded the black population. In fact this is used by Cuban exiles to pretend as if racism wasn't that bad prior to Castro.
Cuba was racist then and it remains racist today. Castro wanted rap banned because too many of the rappers were talking about racism in Cuba.