Yes, the military does look down on Infantrymen. Military Police and other groups will say "I'm just like the Infantry". It's not true. They don't want to be the "stupid grunt" but they want the honor and glory that is due an Infantryman. Remember, while an MP will guard the FOB gate, and the enemy makes contact, the MP will return fire and probably be awarded a medal for it. The Infantryman not only returns fire in self defense, but will pursue the enemy even if it means his death. He normally receives not even a "thank you" for it. It's what's normally expected of him. Clerks and cooks will work 8-10 hour shifts indoors with air conditioning, then go home. The grunt will work 24 hours, in the field, with nothing but the 110 lbs or so on his back, the bugs, the 105 degree heat, the mosquitos, and he'll go home for awhile and then after a short rest, he'll be back on the field.
The Infantryman must run faster, shoot better, and know more about the art of warfare than any other Soldier, save for Special Forces. He must be versatile, adaptable, and multi-talented. He not only has to know how to fight with a rifle, machine gun, or his bare hands, but also how to repair vehicles organic to his unit, maintain and operate communications equipment, maintain his weapons and personal equipment, and provide medical care to a casualty until medics can get to them.
In the Army, we wear a blue cord on our right shoulder signifying that we are a superior breed of warrior. Marines don't have that cord on their uniform, but Marine Infantrymen wear it in their hearts. Make no mistake, there is no tougher or more rewarding field in the military (again, non-USSOCOM). It isn't a job, it's a brotherhood, where your co-workers are closer family than your own wife and children, and will die for you without a moment's pause, knowing that you will do the same. As you progress through the ranks, you will become a father to young men. Not an "E-5" in a support unit, but a "Sergeant" in a Combat Arms unit. The support personnel look on us with equal parts hatred and envy. They tell stories in bars about all of their secret missions. But, as many combat veterans will say, especially of the Special Operations community: "If you talk about it, you weren't there." They want the pride, the glory, the honor, the prestige, the camaraderie. They don't want the hardship, the pain, the violence, the blood, the sacrifice. That's why some Soldiers, Sailors, Airmen, and Marines will discourage you from this field. They'll tell you, "Pick something that you can use as a civilian". That only applies if you're getting a certification, and plan on getting out as soon as possible. Employers usually don't care what you did in the military. I've seen former Infantrymen work for fire and police departments, and former Military Police work in hospitals. Because they lack the courage required to achieve such honors, they'll say and do whatever they can to make sure you don't become their better.
Rotations to Iraq and Afghanistan are common. Expect to go for 6-8 months (Army is 12 months) and come home for about twice that amount of time (Army, 24 months). If you like it, there's ample opportunity to volunteer to go back. It's probably not something you should worry about begging for. Your recruiter can't stop that, or your MOS. Just tell the career counselor at MEPS that you want 0300 (Infantry).