At the top of the library window when you're looking at thumbnails is a filter bar. If you don't see it, press the backslash key.
Under metadata you can choose file type to see just jpegs or raw files.
I think the easiest workflow would be to import everything and then delete the raw files that you don't want to keep. Using the filter as Tom explained would help expedite things.
In the Library module, in Grid view:
- Make sure you have the Filter Bar showing (View > Show Filter Bar, keyboard shortcut "\" )
- Click on :Metadata" in the center of the Filter Bar.
- In any of the columns, hover over the heading until you see the double arrow, and click that to open a list of things that you can use to filter.
- Choose "File Type"
- Click any of the file types shown to filter on that type. You can select more than one by Ctrl/Cmd Clicking.
- When you're done, click "None" at the top to remove the filter.
Thanks to all of you, quick responses!