Hi Robert,
I was there last February, so I don't know the present situation. You could try to email the hotel termales del Ruiz, which is situated in the National Park. I went on a tour from Manizales (can't remember which travel agency), which ends at this hotel with hot springs, after going up the volcano to 5100m, most of our group totally underdressed, with many Colombian holidayers first time on a high mountain. Good times! The hotel is I believe also used as an acclimatisation stop, so they must know the guides in the area. Here's the link, I hope the email adresses at the bottom work:
http://hoteltermalesruizgo.es.tripod.com/ Save travels!
Nick