I'll assume you've seen the TV show MASH? Mobile Army Surgical Hospitals were created in 1945 and were first used during the Korean War. At the outset of the war, you'd have no chance really. The North Koreans advanced too quickly, there were no US forces in Korea until after the war started, and even then, they were defeated at Suwon/Osan, and Daejeon, before the Pusan Perimeter was established.

Some of the first medical personal who arrived went to Daegu, just in time to be evacuated back to Pusan. Once the front stabilized, they went back to Daegu and began working around the clock. They weren't set up in tents like the TV show, but they took over an old schoolhouse.

Once the breakout began, if you were injured, you'd go to an aid station for treatment, and if required, off to a MASH unit, and possibly on to Tokyo and back to the US, depending on the injuries. Patients were carried in ambulances, but also by helicopter, the Bell H-13. By mid 1951, the front had stabilized, so the MASH units were right next to the action and medical evacuations would have been quick compared to previous wars.

For more information about medical care during the Korean War, check out the Office of Medical History.