I don't think it would be too tough to hold that position. Stairs are the walkers' enemy. They just have to worry about other humans and I don't know how many would be too interested in heading into the city.
As for the episode, I was finding myself thinking "I hope this goes somewhere soon" throughout the episode. It just feels like pointless filler. At least last year the random one off episodes for each character helped to further develop those characters. This one really didn't add much. We already know enough about Beth and other than the kid, I don't think we met anyone who will be around very long. Maybe they save the doctor too. He'd definitely be useful.