This bug has been opened here: http://bugzilla.ubuntu.com/show_bug.cgi?id=15173

"Minor, but in the About Me capplet, in the home address section, filling in the
city and then hitting the tab key sends you back to the street address instead
of to the postal code field. That's inconsistent with the rest of the fields.
...
http://bugzilla.ubuntu.com/attachment.cgi?id=4178
Set accepts_tab to False for the two Address fields

This is the simplest solution, since I can't figure out how to set the tabbing
order in Glade. Turn off the accepts_tab property (there's very rarely any need
for a tab in a street address) and the focus moves between input fields with
the tab key. Not quite in the order expected, but it at least it does. "