Galaxies are not evenly distributed. But for all I know this is an unusually sparsely populated part of the sky. Still, your number could shift in either direction by quite a lot.
That is an excellent point. To further refine the estimate we need measurements of the number of galactic clusters and their various densities. For example, in the Local Group (Milky Way, Andromeda, etc) there are about 50. The Virgo Supercluster contains over 2500. Getting those estimates is beyond me at the moment.
Galaxies are strung out across the universe along filaments, with vast voids in between. The voids are mostly empty and very cold, but recent observations have found hot spots in some up to millions of degrees. Overall, the universe has a soapy appearance, i.e. lots of space with the "stuff" strung together.
One thing to note is that, at least to my knowledge, there are galaxies in all directions. There may be voids along the way, but you'll always see them closer or further away.
One of the reasons that this ESO deep field view is important is that its bigger than the original Hubble Deep Field, so we can start answering questions about density and distribution.
