I also put our Facebook information in the move in folder, and mention it during the move in process. We post more than just photos. I also use it to post lost and found items, early closings, holiday hours and resident events, and encourage people to like the page for that reason.
I have attached our sheet to this reply, please use it as template if you like! :)
Facebook is also a great tool to find your demographic. Using the detailed tabs I know that of the people who like our page, 30% of them are ages 25-35. Knowing your demographic can help you adjust your marketing methods, among other things.