The higher you dose on LSD, the harder it is to hold a train of thought, and the same applies for conversation. If you want to talk to people while on acid, take a lower dose or just get used to the experience through numerous trips. But if you're looking for a substance that isn't so distracting, I've heard 2C-B gives a very lucid mindset. Consider mescaline too, which is also a phenethylamine - and the only naturally occurring psychedelic one.
I once had my landlord walk into my room and start asking about rent while I was in the middle of a peruvian torch trip. What's worse, her clothes were colourful and patterned, so of course they were morphing in the most fascinating ways. Even more, she was a former psychonaut herself who's now turned against all drug use, so she'd be able to pick it better than most people, and doesn't approve of it in her house. Not only did I have a perfectly normal conversation with her, I even followed her back to the kitchen afterwards and started talking philosophy (which is something we often did sober anyway), and she never suspected a thing.
However, I suspect I'm unusually resistant to mescaline, as I've taken amounts of up to 21 inches and never had more than light effects. Still, a light mescaline trip is a lot less 'inebriating' than even a threshold LSD trip.