I have it working now
When a user is not logged in and a zip code is entered the package type used is from the international shipping package type option...regardless of the fact I'm using a domestic zip code.
When a user is logged in it recognizes correctly to use domestic shipping package type option.
Essentially, I had different shipping package type options selected for domestic vs. int'l but had limited the results to only show the shipping package type that was set for domestic. Hence, since non-logged in users are by default treated as int'l based on your code (regardless of a domestic zip code) no returned UPS results matched my settings.
To replicate this only allow for UPS Ground shipping under "Select authorized shipping methods". And under "Pick-up and Packaging" set domestic shipments to "package" and int'l shipments to "UPS Express Box". Now remain logged out and add a product to cart and enter a zip code domestic to the ship from of the product.
FYI, to figure this out it was helpful for me to see the xml generated by the shipping module debug, but as regular VISITOR (non-admin), meaning I had to find and remove your admin checks for debug output. Might consider removing that check or adding it as an option.
Thanks again for the help and this most excellent mod.