The “Site actions” text is set by the “text” property of SharePoint:SiteActions control in master page.

The text property is not editable, it is read only.

I have done this in a different way. Here is the alternative solution.

You need to create an image which includes the text you want to show instead of actions menu.

Open master page in SharePoint designer.

Select “Manage styles” pane at the right hand, if you don’t see it then  click “task pane” and go to “manage styles” from menu bar od SharePoint designer.

Select “.ms-siteaction,.ms-siteaction a” , double click to open core.css which only applys to current site.

Add  the following code to the tab.

Font:0px;
Background-image <url of your image with text>
Text-decoration: none;
width: 50px;
height: 20px;

The width and height could be change according to your requirement.

Now save the changes in core.css and go back to your user interface of your site, the text will be replaced by the text you defined in the image.