When focusing very close with a macro lens, auto focus has a tendency to "hunt" (not find a proper focusing point, making the auto focus feature pretty much useless for closeup shots.
With the NEX series of cameras you can achieve manual focus easily and quickly using the peaking (highlighting areas in focus in a different color) and assist (magnification) features that are built into the camera.
Another option is using an old manual focus "standard lens" (50mm or thereabouts) with extension rings (or "tubes"). These rings mount between your camera and the lens, making it possible to focus much closer. You can find a set of no-name rings on eBay for less that $10. This way you can have a 50mm manual focus lens which is great for portrait shots and also use it for real macro photography. You can find a Minolta MD Rokkor-X 50mm f/1.7 (beautiful little lens) for $30, a Minolta to NEX adapter for $15 and a set of macro rings for $10. It is a nice way to get into macro photography and won't blow up the bank.