The text for that link comes from resource files so it can be localized.
I've just implemented a config option to override it so it can be customized rather than localized. In the next release you wil be able to add this to Web.config or user.config
<add key="MemberListOverrideLinkText" value="Employee List" />
Its in svn trunk and will be in the next release.
Alternatively, for an immediate solution, you could just view the rendered source of the page grab the markup for the li and a tags containing the link and paste it into your layout.master in place of the <portal:MemberListLink id="MemberListLink" runat="server" RenderAsListItem="true" />, then edit the text for the link.
Hope it helps,