Two friends and I signed up for the afternoon group tour that involved walking and a shuttle bus. I really enjoyed learning about the history of legal street art and looking up close at beautiful graffiti around the city. Following the tour, I purchased a neat illustration at the Post Bar gallery from an artist named Malatesta.
My only gripe is that registering for the tour was a slight pain. Rather than having an online form listing dates, times, and locations, you have to email Graffiti Mundo to figure out tour availability and the meeting point. I wasn't connected much to my email during the trip but had to keep an eye on it to confirm the tour details.
I think these tours would be even more popular if the sign-up process was easier. (This, of course, is coming from someone who works on website design and user experience for a living!)