If you join up, no matter what they tell you you're going to be doing, you should still expect to deploy to the desert for up to 15 months at a time. If you go as an MP, you might expect guard duty. But it's also possible you will deploy to augment another unit and be tasked outside of your specialty.
Before you join up or sign anything, you really need to contact the local units and find out what they really do, what their ops, deployment, and exercise tempo is, etc. At least in the USAF, there is no such thing as a "support" airman. Even the refrigerator repair specialists are deploying to the desert for convoy duty or other combat / combat support roles. My cousin got called back from nursing school and a commissioning opportunity to deploy to the desert for a year as a vehicle mechanic...