We don't currently have a dog, and if we got one the cleaner would be introduced to him as a puppy. She is a dog lover, so I don't foresee a problem.
In the past, when we had a dog, he was a friendly soul, and got to know the cleaner before she started coming when we were out, so again, there was no issue. The house was busy then, with two teenage children and their friends in and out all the time, so the dog was very sociable.
I think that it's the same for a dog as getting to know anyone who comes to the house. I would spend time with both the dog and the cleaner together, then be there when the cleaner lets herself in and be positive about it. You know your dog though - if he isn't friendly or is very territorial you might be better off asking the cleaner to come when you are in. Oh, and you should absolutely let them know in advance that there is a dog in the house. They may be allergic, phobic or just not want to deal with pets.