Depends on the pleco and what else is in the tank. Some people in the forum keep carnivous-type plecos in acrylic tanks; these types look for food in the gravel rather than rasping on the acrylic/glass. Those that are more herbivourous will eat the algae on the acrylic wall, and in the process scratch the acrylic. Then some folks have herbivorous plecos that like algae, but stay away from the tank wall for whatever reason. So there are some individual differences in the fish itself.
It sounds like you have a common pleco. At that size, they probably are more interested in pellets and are somewhat carnivorous, rather than algae. May be ok. I'll defer to someone who keeps commons.