The Mombacho tour I have taken with Eric Tours was wonderful and left me with good impressions overall, but doing it on the weekend was my mistake. At the weekends it is extremely overcrowded there! Although I did it with a tour guide, he still had to pay at the entrance and we ended up waiting for about 30 min before he could make it. Then the truck that took us up was about 40 min late because, again, the park does not allow to come with small cars.
I read some people criticizing the safety of the truck and I should say that if safety is your concern, you better not take the truck (although I enjoyed the ride and thought it was dun!). I ended up being the first, so I got the most "comfortable seat"- it is just a metal box with metal chairs. The truck was cramped and many people were standing. On the way back there were around 50 people where only about 30 could be seated. On the steep hills, I often had a feeling that it was going to stop and roll over :-), but the driver was quite professional!
So, safety is not there, but it is still fun.
Many people were walking but they looked quite desperate as it is a REALLY STEEP walk.
Then when we got to the visitors center, it was again overcrowded, but still the guide made quite nice explanations about some reptiles of the area, there are some butterfly expositions and a great imitation of the volcano. The walk around the crater was lovely and easy. The views were really gorgeous! We could see the Nicaragua lake, the Apoyo Lagoon, Granada, some other volcanos.
While walking around we also saw one sloth, one monkey and two red eye tree frogs- which were so colorful and pretty. But because I there was only one species of each animal, and we could all stop and look at them, I was wondering if they were really the wild ones :-).
I will not tell how we fight for seats on our way back (remember, around 50 people for around 30 seats). The driver reluctantly dropped us at the coffee farm (I insisted on it as it was a promised part of the tour and I had to remind that I paid for it). At the coffee farm we could taste really delicious coffee (I am not fond of Central American coffee, but this one the best so far and could be compared with the Colombian coffee, so I bought a few bags- you can pay with a credit card).
My guide showed me around a bit and explained how coffee is grown. Then the tour company's car had to come pick us up because the truck did not stop at this point and it takes really long for it to go up and down.
They also have two canopies in the park. I did the one that is before the park entrance. It was fun but they really quickly pushed me through it as I was alone. Probably, the one that is right by the coffee farm might be better.
I would recommend doing this trip by yourself, it will be cheaper and you will be able to stop as much as you want where you want: and you will always be able to hire a guide at the visitor center.