Is 1830 a good place to start? It's the one that I see for a reasonable price most regularly.
I'd like to think I could get someone to play it, but it's probably going to be a solo venture at least until I'm happy to teach it.
I was eased into 18xx by an experienced partner. He feels strongly that 1825/29 (which have a less predatory stock market) are the best games to start with. Of course, they are expensive and hard to find.
After he started me on these, I bought 1830 off of Ebay and played it with my son. It was fun. Neither of us knew enough to make it really ugly, but my son was definitely getting the idea (and he beat me, of course). For a group of all newbies, I think 1830 is a fine place to start.