I've basically done the exact same thing as you (though I was there for a different conference) and pre-organizing meetups online is essential, you just don't r

I've basically done the exact same thing as you (though I was there for a different conference) and pre-organizing meetups online is essential, you just don't run into people, as you noticed. Even if you go to somewhere like Red Rock Coffee it's jam packed with people busy working on their thing, so you'd need to be pretty forward to strike up good conversations. nl's advice seems to be broadly on the money. Get in touch with people online first, and also spend more time there so you don't have to pack the schedule too hard.