I don't like to play around with card as there is always a risk of something happening to the card and then all the images are corrupted. I just transfer all the images right away to my HD, then work from there.
I do almost the same thing, but I don't use LR to sort and remove the images I'll discard. There's a great Mac app called "Xee" that makes selection, trashing, moving and/or copying easy. Here's my workflow:
1. Copy the card's image folder directly to my storage drive.
2. Run the photos thru a renaming app ("A Better File Renamer") that renames all the files with shooting date, file number and camera used. Just drag the folder to the application icon and it renames 'em all. This allows Finder to easily store and locate any file on any of my storage drives without having to launch an asset management app like Lightroom, Aperture, Elements, etc.
3. Open the copied folder with "Xee" and review each file in full-screen mode.
4. Trash any file I don't want to save (using just a simple keystroke combination) or -- with another keystroke combination -- copy or move anything I want to process in some special manner.
This leaves only images worth keeping in that imported folder. I then rename the folder to some name that will be memorable. The whole process takes no time at all and, except for actually examining the images, it's completely automatic.
You can find out more about Xee and A Better finder Renamer at macupdate.com