Remember when commands are given to a dog, he has to interpret your native language as well as your hand and body gestures in order to comprehend those commands. With that being said, it could be then concluded that dogs will understand a command in any language which it is given to him. It would be much easier for a pup to understand commands in different languages that a adult dog, as the pup is in explore and learning mode and his/her little mind is blank and soaking up bits and pieces of information.
But mature dogs can somehow understand the bilingual commands of any owner once those dogs are trained to understand such commands. So let us say that Maria is a Cuban national who now lives in America. Maria is a great animal activist and owns two dogs herself. Like most bilingual persons, sometimes they switch between tongues and normally speaks their native language when excited,frightened, overwhelmed want to say something they think you will not understand. But what they don't know is that the dog is also soaking up as much as the language as possible. So if maria comes in the room and gives the dog an order to sit. She probably would say "Sientate bruno" which translates to sit bruno. Or she may just say "sit bruno.
Which ever command is given, you can be assured that the dog will respond with the appropriate action. Once the owner reinforces the word with the action required, the dog will fuse with the language very easily. You could say that dogs understand different languages very well and maybe multilingual