Transport situation in Seoul

Hi

I am going to teach English in South Korea next year and am trying to get a job in Seoul. I was wondering how far I could live from the school - what are my options, should I get somehwre as close as possible even if it is expensive? Hhow long does it take to travel on public transport? Is it likely to find somewhere within walking distance? Also, how do people who don't speak Korean get around - are the signs and maps in English as well? I know Seoul is supposed to be huge (I've seen some pictures) but I'm from a small town so it all sounds a bit overwhelming.