I don't know why I didn't think of this before. Historically I've always used the Flag function and marked photos with a flag that I wanted to send to Flickr. The workflow was simple, flag photos, filter by flag, export to Flickr. Then, my world was rocked because I realized that flags in collections are unique to the specific collection. Ugh.
The solution is obvious and way better. Create a top level collection called "Flickr" and then create collections inside of that for each photo set that you have on Flickr and drag the photos you want to publish into there. Much better solution, plus you get to see the Flickr/Lightroom sets in both places very cleanly.
Cool.