I've kept angels with common plecs & bristlenose plecs, never had a problem. Dime size to adult angels, with inch long bristlenose to a 15" common. Plecs & discus can be a problem from what i've heard, due to the increased slime coat on discus.
I've got 4 plecs and 6 angels - never had a problem. I've read about problems with plecs sucking flat sided fish, but it tends to start when the plecs are starved of a good diet (eg. left to clean up after other fish without food of their own), then develop into a habit. If you feed the plecs a good diet then it shouldn't be a problem