We climbed the mountian with Runa Tupari Native Travel (http://www.runatupari.com) and payed 60US for 2 days (native Guide, food, transportation, tents, mats). Very cheap and good service altough they don't have the equipment to go all the way to the top (final 50-100m).
Just a few notes that may provide more info on climbing Cotacachi. One can hire a caminetta (2wd pickup) from Otavalo or the small town before the lake for about $50 one way. It will take you to the antennas and cut off about 1000M of climbing on a badly washed out road. The climb from antennas (about 4000M)to top is close to 1000M. The route is marked very well with cairns down lower but is difficult to follow higher up. A helmet is a necessity due to constant rockfall. Some guide books call it scrambling to the top but others call it class 5. We did not get that high due to rockfall hazard. There are several ok campsites at antennas and further up that are large enough for a small tent or two. The cabinas at the crater lake inside the National Park are very comfortable with hot water showers and fireplace for $12 per night in 2006. There is also a 4x4 at these upper cabinas that will take you to the antennas for $50 one way. The government run cabins on the shore of lake are nicer and include dinner and breakfast for $25/night. Govt cabinas accept credit cards. The lake is at about 3100M and the trail up Cotacachi starts as a dirt road to the right of the toll booth when entering park.
We hiked Cotacachi mid May of 2014 and were told at check in that we were not allowed to climb without a mountain guide, but were told instead to hike the lake. We said sure and hiked the opposite way around the lake for about an hour before getting to a point where the road up to the antenna butts up along the trail. From that point we abandoned the trail and headed up the road for 3-4 hours before arriving at the antenna. Since its not really allowed, there really isnt much in terms of camp sites. There is one area after a walled bend in the road for a small tent, but know that it is not well drained and rains often. When we arrived to the site, 2 military patrol approached us, asked if we had permission (which we said we did) and made sure we had enough clothes and stuff because it was going to get cold. I also happened to be hiking in the company of two blond, fit, gringas and they told us if the weather gets bad we could come into their post which was equipped with internet, heat, etc. After asking a few more questions, they left thinking we were crazy but let us stay without further trouble. We spent the night under rainy and windy conditions, but awoke to a beautifully clear sunrise, which alone made it worth it. After sunrise, we had a quick breakfast and started up to the peak, planning to ditch our bags before the final ascent and bag it light and quick. Along the way, we reached an opening with a picture of the virgin mary, and then the clouds set in pretty thick. At that point we decided to abandon the trip and start our trek back as visibility was minimal and didnt seem worth it. The peak stayed shrouded for the rest of the day. We had been living in the valley below the volcano for several months before the attempt and it clouds in quickly after sunrise 95% of the days. The sunrise was worth it, but summiting in clear conditions will be a rare event.
Time on trail around lake: 1hr 15 min.
Time on road to antenna: 4 hrs.
Summary: Guide needed unless you want to break some rules. Sunrises are usually clear and the views are incredible.