How to override the ['search_distance'] in Location: Distance / Proximity Views in a custom module
I haven't had much experience with Location module. This feature is supported out of the box with Openlayers module. I would recommend checking out that module.

I have done a similar sort of thing for one of my clients. I had to hide the distance fields as they didn't want that. If you view source you can see those fields in HTML.

http://biopetonline.com.au/stores