Are they wanting something that comes off easily and cleanly? Or are they wanting a reusable material like static cling?
Most vinyl (including calendered) is removable - depending on the surface applied to. We would use Oracal 3640 for cheap, short term applications. The main issue we had was more adhesive residue is left behind which has to be removed. Something like Avery's 1005 SC series comes off a lot easier.
The only vinyl I've personally worked with that was NOT removable is the reflective. We had problems on a couple panels for a reflective real estate sign, and it took HOURS to clean those off. For what we spent on labor, we should have scrapped the panels and just gone with new ones.