Deltas and Facebook

For the past 6 months, I've come to build a few relationships with some Deltas whether through community service, work or school. Normally I would add my relationships as friends on Facebook but now that I've expressed interest in the sorority, I'm afraid to add some of the Deltas for fear that my intentions would be misinterpreted. Many of them, I've grown to like and enjoy on a personal level so I don't want to send them the wrong impression. Should I go ahead and add them or wait until they add me?