The first thing that struck in in your request was about the "normal age" for walking being 11-12 months. My pediatrician commented that when both of mine were walking in that time frame, that it was early. She said that with babies sleeping on their backs, the average age for many physical milestones have changed in recent years. She said walking around 12 months is like walking at 9 months used to be when we were babies. She said the norm for walking is more like 15-18 months now.
You said your son can take a couple steps but isn't choosing to walk - sounds like he feels he can be most efficient with movement when crawling. I personally think they progress to the next skill when they find it to be most convenient. At some point he'll be holding something or become confident enough that walking will be easier than crawling and he'll choose to do so then.
Use your instinct - if you feel like he's ok, then just watch and make sure he's continuing to develop physical skills. If you notice other things that concern you as well and feel uneasy, then talk to your pediatrician about taking steps to check into it.