Usually (at least in the social circles I spend most time in), the way to get to know people is to subscribe to them, then comment occasionally on their entries. They'll notice you, probably reciprocate, and then you'll gradually get to know them. Some people consider it polite to drop a comment on their top entry when you first subscribe, just introducing yourself. However, given that you're new to Dreamwidth and need an answer fairly quickly, PMs to random people with that interest could well work.

As far as robots go, you could also try one of the general programming communities, or maybe science, as that will have a fair number of overlapping interests.