As long as you properly feed your pleco (you can read more about that in the Pleco sub-forum, it's a sticky, good read) then I believe it to be okay. Maybe smaller plecos would be better than big plecos, or plecos that turn more predatory as they age.
Otos are a good alternative, if it's for algae reasons. Honestly, discus need pristine water, and barely any nitrates, so adding a pleco may just be more work than it's worth, since they dirty a tank as much as they do.