The pleco will need some hiding places if you've got him with a Jack Dempsey. I've kept the bristlenose, clown, rubber lip, and currently have the king tiger. All stayed fairly small. Out of those I've kept, the rubber lip was the most fragile. Contributing to that was the fact that they come from really clean, flowing, cooler water than my planted tank with angelfish wouldnt have. Further contributing was that I always got them from Petsmart. They would likely do better if I got them from a smaller lfs
The bristlenose were bullet proof practically. I had to give them away though since they were chewing holes in my plants. They got bigger than the rest, but still less than 6 inches. They did a good job on algae, but an even better job on plants....
The clown is a pretty cool little pleco, but they eat wood, and a lot of it. Expect to have a ton of wood pulp-like waste all over the place. He never touched algae that I could see.
My king tiger is a neat little guy, but I rarely see him. I've had him for a few years, and see him only once a week or so. They're mostly meat eaters, and so they go after beefheart and bloodworms like there's no tomorrow. It's a good clean up fish for the angelfish. I had him in a discus tank for a while.