yes that will work as it will be just like a normal link. Only the image will open in a new window (or replace the current window) and that is exactly what is not supposed to be happening on the Plus! site.
It all depends on what you mean with "opening an enlarged image". It depends on what you want to do and how you want it to look to the user.
----
btw using
<a href="blah.png" title="Click to enlarge"><img src="blah.png" width="100" height="100"></a>
is a very bad method as you will actually always load the entire image. If the image is a 2MB big picture, the user will still need to wait a very long time, even if you put 100px as the dimensions. The dimensions do not resize the download of the image, the image is still downloaded fully. Only it will be displayed a bit smaller.
Much better is having two images, a thumbnail (100x100 px) to show to your user, and the original big one (1240x1240 px or something whatever) to show when the user clicks the thumbnail
<a href="blahBIG.png" title="Click to enlarge"><img src="blahTHUMBNAIL.png" width="100" height="100"></a>
/ 
