See this link from Social Security's Frequently Asked Questions (FAQ) page: http://www.ssa.gov/deposit/DDFAQ898.htm
Here is the relevant portion:
After I sign up for direct deposit, do I have to stay with the same bank?
No, you can use direct deposit at any federally insured bank, savings and loan or credit union. If you move your account, call Social Security's toll-free number, 1-800-772-1213 (TTY 1-800-325-0778), and a Social Security representative will change your direct deposit information. Open the new account and make sure your deposits are going to the new bank, savings and loan or credit union before you close the old account.