I'm sure I'm going to start sounding like a Walmart pusher, but I tend to buy a lot of my plants there. If you find out what day they bring their fish/plant orders in, you can have first pick of whatever's popular that week. This week here, they brought it mostly swords and rotala, along with their weekly tithing of banana plants. They sell for about $5 a plant (Canadian) and if you get there early in the fish week, before they've been mauled by the fish or the employees trying to net said fish, then they're usually in good shape. They come with little tags that tell you the name of the plant as well as care instructions.
That being said, the selection is limited, and if you want something specific you're better to get it online or from your LFS. When I decided to ditch plastic and go real, I bought a couple plants at Walmart (banana, sword, moneywort) and then got the rest at my LFS, where they had a "bunch plants, 3 for $10" sale. Granted, they were on sale because they were getting a little weedy and torn up, but a little love and a lot of light and fish poops, and they sprung right back up.
I live in an area of Nova Scotia where there's nothing I'd really call a "lfs". We have Walmart, Pets Unlimited (expensive), another generic pet store in the mall with a limited fish section and a couple plants, and a pet store across from the mall in a little closet of a building that doesn't seem to have anything you want at any given time. I tend to subscribe to the theory that buying plants and fish from Walmart isn't for those new to the sport, but if you already are educated and don't need the employee to do more than net the fish, then its a decent place to rescue some critters that would otherwise end up dead in a bowl.
