Yes (provided you don't insert full-width versions,* of course): you simply set the alignment of the images to left instead of none.
* When you are about to insert an image, you get four size options: full-width, large, medium and thumbnail. Full-width means original size, if the original is narrower than the main column, or downsized to the column width, if the original is wider. The default widths for the other three options should be set by you in Settings > Media. The width of the main column in Twenty Eleven is 585px, so you should set large, medium and thumbnail to around 500, 300 and 150, respectively.