I have heard that is a no-go unless you get one specifically mandated food-safe. There will be sites that say to do it, but there are also sites that say you can use normal rubber stamps on cookies for aluminum flashing from the hardware store to make cookie cutters, which are both proven to be not the way to go.
Here is sometbing I found on the subject on a how-to bake in terra cotta flower pot:
Choose a terra cotta pot. Search for untreated, food-grade terra cotta. You can find these at specialty food and baking stores. Avoid those from gardening and hardware stores because these may include unsafe elements or may have come in contact with toxic
Here is the full link:
Here is something from Kansas State University Research & Extension Agents:
Are terra cotta flower pots safe to cook or serve food?
Not recommended. Flower pots may contain lead. They are not made from a food safe material.
I would play it safe and if you can find the manufacturer's information, I would call and ask them if it is deemed foodsafe.
If it helps, I recently found small silicone flower pots expressly for baking at Michael's. They are part of their new Mary Engelbreit collection and they work very well with cupcake size treats. I tried to do a search to get a link to show you, but I could not find anything. They aren't cheap, but the Micheal's 40% coupons helps a lot.