How to create a pseudo-guest account in Lion with FileVault 2?

Solution 1:

Guest Account

This account is visible in Directory Utility, but please do not attempt to make it compatible with FileVault 2. Not only for security; there may be other good reasons for Apple making this account not available whilst FileVault 2 is enabled.

Other accounts

For your guest you might like to create a standard account, or add parental controls. You can probably have an account that is password-free. This is in line with Kyle Cronin's answer to a linked question.

Recommended reading

Apart from being able to encypt an entire volume, what are the other differences of FileVault 2 over FileVault?

Solution 2:

If you download the OS X server tools package, you can use the Users and Groups application to modify user's rights, even on OS X Client.

There are quite a few options to lock it down in various ways, depends on your exact requirements for locking it down.

So, I would just create a regular account and configure it to run the way you'd like.