Clear a few questions up.

Good afternoon Marines. I'm an open contract waiting for the job dump in October. When I was a Sophmor I was dead set on the Mp field. However I was only looking into that for the sake of my father who was dead set on me not enlisting so I told him i would stay out of the infantry field originally. Realizing its my life I've decieded to go with what I want. What do field Mp's do? I have searched all over the place. I think from what information I have gathered they train and deploy with infantry units. And garrison Mp's are just like the law enforcement agencies in the civilain world. Am I correct in these conclusions? Also is there anyway I can pick which division of the Mp field I want. Because if not I might as well just go Infantry.

Field MP's are basically mounted(in vehicles) grunts. On a deployment you would run security for logistical units/convoys. I recently deployed and was attached to a Security Platoon which was all field MP's. We spent about 90% of our time in Afghanistan outside the wire doing PSD(personal security detail) missions for a few Generals, Colonels, and their enlisted counterpart. When not doing that we were running route clearance, route reconnaissance, and security for all the logistics convoys running through our AO(area of operation). And yes the garrison MP's are the ones who post at the gates, check ID's, enforce laws/regulations on base, etc...basically a cop.

From what I am reading in your post I would just suggest going infantry if you can and if that is what you ultimately want.

There are the new 'Law Enforcement Battalions' the Marine Corps is talking about putting into place that will be doing all sorts of oddball 'police' type stuff....but don't expect to be doing traditional LEO work on bases any more. Most bases have civvie cops doing that sort of work now (Google 'Marine Corps Police'), the military has just about gotten out of that sort of thing. You won't even be standing a gate, since those are either contract guards or other civvie types.