I wanted to do this as well.

However, when I edited the file I saved it over the original one, I stuck it into both templates since it seems some files are being use by the default one:

\includes\languages\template_default\product_info.php
\includes\languages\wallet\product_info.php

The problem is that neither are working. The page still displays "Please Choose"

I am using v1.3.8 I have installed the wallet theme. I have no idea what can be messing this up. It looked to be an easy fix/edit.