I got there at around 2:00.  That seemed to be a good time to arrive: there was a medium sized crowd on the floor, but there was a steady flow of people filling the place up.  John Creamer was the guest dj when I was there, and he came on at around 3:00.  I'm not sure if that's exactly when Howells will come on, but you can bet that he'll come on in the mid-afternoon once the place has filled up a bit.  It seems to stay open fairly late (at least until7 or 8), so I wouldn't worry about getting there super early.