What Pleco's won't tear up plants? I tried one once before and he thought my tank was an all you can eat salad bar. I have heard that some don't eat plants though.
Plenty of them don't eat plants.
Some have a natural taste for plants but most won't resort to plant eating unless there isn't enough to eat otherwise.
Ancistrus sp. (bristlenoses) are very polite tank inhabitants.
Parotocinclus jumbo. It's an oto-like plec. Very nice. Though I've never kept them I've known those who have and I've never heard a mention of them being plant-eaters. I almost bought some of them for myself. They're really cute!