No shoes is supposed to be better-they can actually "feel" what they need to do with their feet, but I think that's for a child who doesn't walk at all. I think shoes or no shoes may not matter for your son.
I love the idea of taking your son to the Regional Center. They can be called things in different cities, as the other poster mentioned. Here in San Diego, it's called San Diego Regional Center (which is easy, right?) but when I first used one I was in Little Rock, and it's called First Connections there. If in doubt, type in your city (or state's) name and "developmental delay" in a google search and something should come up. It's through the state health dept, so if all else fails, just call the main number and explain what you're looking for.
Here's why I think the regional center is a great idea. It doesn't mean you're worrying about your son or disagreeing with his doctor. However, because they give really thorough evaluations (my son had a speech delay), they'll pick up on things that you won't. And honestly maybe you're doctor wouldn't notice in a short visit. If your son doesn't qualify you're no worse off than you were, but if he does you'll benefit from 2 things: 1) a PT or OT working with your son 2) they'll work with you teaching you how to get your son to walk consistently.
In addition to a Speech Therapist and Occupational Therapist, I got a behavior counselor (I think that was her title). She met with me once a week for 8 weeks and taught me how to modify my son's behavior. It was whatever I wanted (leaving the playground when I said it was time, potty training, transitioning activities). This was stuff that any mom of any child would love to know. It was great information that really had nothing to do directly with his speech delay, but once you qualify through regional center there are all these resources that are awesome!
Good luck to you! Let us know what happens!