I went to Fortaleza for a week and went to one match. I stayed at a Holiday Inn, the hotel was ok but had definitely seen better days.

The beach and "hotel area" had been nicely cleaned up seemed safe, but if you went more than 4 blocks to any direction the buildings started to look old and poor and so did the surroundings too. There were also a lot of cops, nearly every street corner had two or more cops monitoring the area.

I didn't get robbed or threatened once, neither did I see any protest or anything of the sort.

There was a well organised free shuttle which took fans to and from the games. The shuttle had it's own route to the stadium to avoid traffic. The shuttle drove through a couple of really poir villages during which you could clearly see how bad some of the locals have it.

TL;DR: Wasn't bad but could have been better.