This is a tough question, since it depends on the configuration of the encryption client :)
I assume that the files were encrypted with the Removable Storage version (since this does a file based encryption instead of the Full Disk / Hard Disk that does it disk based). If you configured the client to include a recovery certificate, then yes you can try that to decrypt the data.
In case you (or actually the person setting up the client in the first place) did not configure this recovery certificate, then you are in a painful situation. Only trying to remember the correct passphrase will make it possible to recover the data.
How to decrypt removable storage files using a certificate which are encrypted by a user with a password and the user forgets the password or the password is lost?
http://www.symantec.com/docs/TECH163363