The seating capacity in there is about 50 and some of it is at tables and bench seats so you may or may not wish to join others at their tables (that means even if you get in, you may not be able to find a place to sit right away).
On weekend nights (Friday-Saturday) it will be busier. I just went on Sunday night and walked right in.
for those who can drink the alcoholic drinks, there is one price that includes the souvenir mug, and one that doesn't. If you want the mug, ask. You won't take home the one you drink out of, they'll give you a clean one in a box when you leave.