All mysql calls are escaped so injection should (hopefully) be covered.
I'd make a habit of using prepared statements exclusively. No handcrafted SQL queries. All your parameters are sent as binary (or escaped automatically in some libs) and there is no need to escape. If you handcraft SQL queries there's a small chance you'll forget to escape something.
Agreed that if you are storing information that is sensitive (such as email addresses or other more personal information) then it should be encrypted.
This makes zero sense if the decryption key is stored on the same server.