Question about Marines?

I've got some questions about the function of the Marine Corps. A lot of enlisted Marines i have talked to said that the Marines are infamous for not giving you what you wanted out of it, (specific jobs, advancement, special schools etc.). I understand that they arent in business to please the basic grunt, but am i really powerless over my Marine Corps career? I want to go Infantry, and i want to give Recon, S/S, and Force a shot if i qualify. I also want to be deployed to the Middle East (if im joining i want to at least be in the fight), how do they decide who goes there and who goes everywhere else? Will i be totally screwed and told, "Nope, you are going to load trucks for your deployment, in Okinawa." Any Marines here have any comment, did you get all you wanted out of the Corps? If i avoid behavior infractions and display maturity, will i have a better shot of being allowed to try for these units or receive promotions? Thanks all.