I'd be interested to hear what the conversion rate is like i.e. people coming to the dojo from these sources
I don't think Facebook is very useful to drive students to the dojo if what you are interested in is generating membership. Aikido Eastside is a major "training center" which has folks attend events from an international. We are holding 14 major seminars this year, which far and away exceeds the ability of our students to support all our events. In order to have such an aggressive schedule we really need to have a significant number of folks coming regularly from outside.
This requires a lot of promotion. I can't just put out a flyer and forget about it. Facebook allows me to build a huge community of folks who "follow" my activities and the dojo events. That's what it's good for.
Generating membership is quite a different task. The vast majority of your students come from within a 20 - 30 minute drive at rush hour. Anything outside of that and folks REALLY have to want to be there. So the reach of Facebook is fairly useless for that. Working the Search engines like Google and Bing are the best ways to reach potential new members. I will write an article about that soon.