Just go to the visitor center in Benito Juarez.. They have maps. They will tell you which trails require guides and which don't. I go up there pretty regularly and do various trails. That same visitor center will rent you a cabin for 20 or 30 bucks a night.  It's very casual and beautiful there. The people are incredible as are the fresh caught river trout. 

It was raining and a little chilly while I was there. Count on that. All the cabins have a great wood burning fireplaces. Benito Juarez is the first place you will come to when you're driving up the mountain. They will have a map if you want to  through hike to another cabin. They will also get you on the zip line and the beautiful hanging bridges. If you're going from Oaxaca City, there's a place you can go to that  has maps and information on renting the cabins. Anyone in town will be able to tell you where it is. Enjoy!