Hi
Sure can. Remember that EFS is profile dependent (ie login dependent), so data is 'unencrypted' when you install etc and you wont have a problem. Other (simulatenous) users can not read any of the files contents though, which is what you need.
Before installation, have a careful read of EFS, profiles and the implications of altering it with EFS enabled.
Cheers
Chris.
Chris Kempster
www.chriskempster.com
Author of "SQL Server Backup, Recovery & Troubleshooting"
Author of "SQL Server 2k for the Oracle DBA"