Hiding All Site Content in SharePoint 2010

All Site Content is located on the Quick Launch in the master page. You will need to edit the master page on usually v4.master or your custom master page.  

              
The "All Site Content" link or button is created using a SharePoint control named ClusteredSPLinkButton. The control can be hidden from selected users by changing the PermissionsString attribute.

For example, changing this to PermissionsString="DeleteListItems" would hide this control from users that can't delete items from a list, documents from a document library, and Web discussion comments in documents.

<SharePoint:ClusteredSPLinkButton 
id="idNavLinkViewAllV4" 
runat="server" 
PermissionsString="ViewFormPages" 
NavigateUrl="~site/_layouts/viewlsts.aspx" 
ImageClass="s4-specialNavIcon" 
ImageUrl="/_layouts/images/fgimg.png" 
ImageWidth=16 
ImageHeight=16 
OffsetX=0 
OffsetY=0 
Text="<%$Resources:wss,quiklnch_allcontent_short%>" 
accesskey="<%$Resources:wss,quiklnch_allcontent_AK%>" 
/>