If Filevault is turned on, and they can't spy on your work, go for it! Just back everything up, because they can lock you out at any moment, but they shouldn't

If Filevault is turned on, and they can't spy on your work, go for it! Just back everything up, because they can lock you out at any moment, but they shouldn't have access to your data. They would just wipe it when you return it.