Ring first, they don't ALWAYS have a full floor of pins, i think some nights have been small turnout and/or cancelled due to a month of high sales and not much left on the floor to play ;-) which is good for biz, but bad for the faith nights hehehe.
Otherwise, it's well worth it, i've been a few times (long ago) with friends, the $25 also covers a few slices of pizza and (soft)drinks & nibbly's too..
On a good night there's 60+ machines and the crowds can vary from 20-120 ;-)