How to make a 2D chart and use letters for labeling?

edit

Here's one way to get what you want:

data = [[1,15],[2,19],[3,18],[4,22],[5,15]]
list_plot(data, plotjoined=True, ticks=[[1,2,3,4,5],1],
          tick_formatter=[['Jan','Feb','Mar','Apr','May'],1])

And here's a live example.