There is a group that slalom boats through the winter - they would usually be using the gates in Lyons, but....that's not an option so they are looking for other options...seems like maybe Golden was a good one. I'll PM you the contact info I have for it one of the guys I talked to about it. I don't know jack about slalom kayaking but have been in touch with this group and they aren't worried about your skill set, just that you want to do it, so there are all levels involved. I hope the email I send you helps out.
"You know that old trees just grow stronger and old rivers grow wilder, everyday..."