T.A.
We had a part time live in nanny Spanish speaking only with us a few months back. We loved her. She is now employed full time by my grandmother. I did not speak any Spanish and she did not speak any English. You would be amazed at how fast my husband and I learned to communicate with her, and she made an effort to learn English. The down side came to what she perceived was ok to let my son do. For Example she was ok making dinner for herself down stairs while my son played upstairs unattended, long enough to get into and destroy the sewing room, pull all the encyclopedias of the shelf and unplug his monitors. From my experience I would make sure you can communicate enough as to what level of care you want your child to have up front. You do have to remember that it is different culture and no fault to my cultures or her culture but things are done differently, does not mean one is better than the other it means you need to be able to communicate you needs upfront in fairness to her and you. I would not let the language with your child and her scare you. He will learn both from you and her and the kids.