They do, unless it turns into open war or bullying, it shouldn't be a problem.
Make sure there's plenty of caves and nooks. Plecs like to have something solid over their heads, and some get cranky if another fish decides to join them. If there's just 1-2 spots they like, they're more likely to get into scuffles over them. If there's more, say 2-3 per plec, there's less chance of conflict, and they might be less possessive of a spot if they do run into each other.
Also, whatever you feed them, spread it out a bit - for example, use two pieces of cucumber in different spots instead of just one. My bristlenose will claim food, sometimes even if he doesn't plan to eat it, and will go ballistic if any other fish tries to eat it. They might have had a scuffle over food, as well.