To find the template to modify, do this - vboptions > General Settings > Add Template Name in HTML Comments > set to Yes . Then go back to your page and view the source code and you will see the name of the template called around your part of the code. (Sometimes the template is the one mentioned at the very top of the page source.)
Then just find the phrase ({vb:rawphrase prefix}) and put a condition around it:
HTML Code:
<vb:if condition="in_array($forumid , array(2,4,6))">Select City<vb:else />{vb:rawphrase prefix}</vb:if>