I have two plecos with my Africans. Just make sure the plecos have some size on them before you put them in. What type of pleco are you thinking about?
I have a common and a chocolate with my haps. Many people keep bristlenose plecos with their Africans.
I have a common pleco in my 180 with few problems. My cichlids have torn his fins, but very infrequently. If any food reaches the bottom he guards it-even chases my adult male kenyi away lol.
I keep a bristlenose 5 inches in my 125 with my large predatary haps with 0 promblems. I had the pleco in there for three years now. The haps ignore the pleco completly, now I have no mbuna in this tank. They could cause a promblem but don't know as I don't keep any mbuna.