You primarily need to consider whether your home state limits the use of that title. If not, you should be able to use it (in addition to "PE") whether you're actually licensed in a state with a title law or not. If in doubt, run the question by your state board and see if they have any input. I know here in TX, which doesn't license by discipline, you can still bill yourself as a "Structural Engineer" on business cards and the like.