Plecos to get to be good sized but a baby should do fine in a small tank. BUT make sure you have a home lined up for him when he gets bigger. There is a great pet store near me that allows you to "trade" them in when they get too big for your tank.

Live plants are good, very good but you need to be experienced, they need more lighting than normal & you have to be careful on what additives you use for your water.