im speaking from inexperiece but there was no dress code at the munch i went to yesterday, so this obviously isnt an across the board thing, surely. id say 9 out of 10 people there had jeans on or were dressed casually. probably a case of finding out about particular dress codes for particular munches and id imagine this would depend on venue, time of day, country, individual organisers and so on. as a newbie, i would not have felt comfortable going to the munch if everyone had to be dressed a certain way because i simply wouldnt know where to start!