The facilities for American GIs were quite nice. The Americans scored for themselves some of the nicest bits of land for some buildings and for clubs and such. While it wouldn't have the same standard of living as, say, a nice home in Boston at the same time period, it would certainly have been nicer than a MASH where they lived in tents and went to the bathroom in latrines and ate army food in a mess hall. Tokyo would have had running water, bathrooms with running water, hot tubs, restaurants, bars, showers, etc. While the city wasn't as built up at that point as it would later become, its buildings were safe and solid and secure. A lot of rebuilding had occurred in the years since the war. 1945-1946 were rough times, but by the time of the Korean war, you could live quite comfortably, even if the poorest residents of the city were still working on getting better housing.