My kids have all been fairly slow to be mobile. Carter walked at 13 months, Sydney at 16 and Derek has no interest yet. He has, however, started to climb the stairs. For the longest time, he would make it up one or two stairs, lay flat, and start to cry. I loved that he was afraid because I didn't have to worry about him. A couple of weeks ago, Carter and Syd ran upstairs to play and Derek followed right after them. It took him quite a while to make it up all 17 stairs but he did it!
He still doesn't chose to climb them very often but when he does, there is nothing stopping him!