Sebastian hasn't shown any interest in stairs. There are climbing toys at daycare, but he hasn't practiced on them. But this morning, much to our surprise, he decided to climb the stairs at our house.
We already have a baby gate for the bottom of the stairs, and we'll install it shortly.
Update - I learned why he started to climb the stairs. Apparently Goober was sitting on the stairs and Sebastian wanted to see him. The cats seem to motivate a lot of Sebastian's movement.