If you're an experienced hiker you will find this trail to be easy, if you're not it will be moderately difficult. You can hike it in less than 30 min if you begin at the trailhead, which isn't as easy as it sounds. There is a parking lot at the trailhead, but it fills up quickly with other hikers and people who are there for paragliding and hang gliding. There are two other lots you can use if you're heading up Estrada das Canoas from Barra, but they'll probably be full by 11 AM or earlier. I arrived at 10 and there was a dude who offered to give us a lift to the trail for R$15. Estrada das Canoas is a windy road and people love to haul ass up and down it, despite the 40 km/h speed limit. Also, there may or may not be a sidewalk, so if you park there and walk up it's a risky venture. If you drive to the trailhead you'll know it when you see the Guarda Municipal at the entrance (they're there on weekends). I recommend at least trying to park here first, people are always coming and going so you never know and might get lucky.
The trail itself is easy. It's not too steep and there are stair-like cutouts for most of it and the majority is completely shaded by trees. There's even a vendor about halfway up who sells Gatorade and coco water. We hiked it in about 20 minutes.
The view at the top is good, but not excellent. It does give you great views of Barra, the ocean, and Pedra da Gávea, which is a much better and much more challenging hike. Because of the ease and popularity of the trail, Pedra Bonita itself fills up quickly with people, kids, dogs, etc. If you're looking for a place to get out into nature and relax - keep looking.
It's an easy day hike though, and is a good way to kill 3 hours or so and is much better than sitting around at a bar or doing other touristy stuff like seeing the painted stairs in Lapa.
One last thing, as an added bonus you can go to the ramp and see people take off in their hang gliders and parachutes. read more