The guards are available from 7:00 a.m. You are not allowed to use this trail on your own. You must report yourself to the security guards and request authorization or wait for a group of people to go up. The parking at "Casa de Cristal" costs $1.00 and the volcano's entrance costs $3.00.
This is a singletrack path. There's another place nearby called "Casa de Cristal" where you can park your car and you can hike from there to the volcano's security guard's house (you are not allowed to go by your own without letting them know you are going to be around, for your own security).
The path is well marked. First you cross a deep forest with some stairs made of woods. You'll find a metal structure lookout; after that, the path becomes harder with more elevation and a lot of small rocks. You'll find two more lookouts with great views to the Izalco volcano. Then you'll find some yellow painted rocks that will lead you to the volcano's crater.
Overall, it's a 3 km trail with about 400m of elevation gain. Depending on the time of the day, you may expect to find deep fog on the top of the volcano. Also, watch out for the rain and the wet rocks when returning down. It's a great trail for hiking or running, adding some elevation. Even though the trail is well made, it's easy to get lost, so I would recommend not taking shortcuts unless you know the area well.