How can I add static text into a Views exposed filter block?
You can do this with Better Exposed Filters.

Enable the module and then navigate to your view edit page.  Under Exposed Form, click Basic, which is next to Exposed form style, and change it to Better Exposed Filters.  Add a Description of "or" to your title.  This will place the text on the page; you will then need to style it with CSS to place it where you want.