The question is a bit old, but let me add a different approach. In addition to the above hot-key approaches, there are default preference settings that can be toggled.
As of Eclipse Galileo (and definitely in my Eclipse Version: Indigo Service Release 2 Build id: 20120216-1857) language specific preferences can open up new files to edit which are already collapsed or expanded.
Here is a link to Eclipse Galileo online docs showing the feature for C/C++: http://help.eclipse.org/galileo/index.jsp?topic=/org.eclipse.cdt.doc.user/reference/cdt_u_c_editor_folding.htm .
In my Eclipse Indigo I can open the Folding Preferences window via : menu/ Window/ Preferences/ Java/ Editor/ Folding
and set all options on so I can open files by default that are completely collapsed.