How can I get ratings of establishments of rehabilation for the elderly in the 11747 area?

You can go to www.medicare.gov. At the bottom of the page you'll find resources. They have a "nursing home compare" link as well as other links that may help. If you want to go to the county website of the Zip code you mention, you will likely find information on the facility, as well. Be aware that they are not likely to totally agree as different criteria may be used. Visiting the facility and making your own judgment may be your best way to assess the place. Check out the staff and how they interact with the residents and with each other. Talk to family members. There's nothing like firsthand knowledge.
Take care,
Carol