Give yourself plenty of time to order. If you are lucky you might find street parking, otherwise, plan on parking in one of the nearby parking structures. There will be a line on the sidewalk since the store is small and they can only let so many customers in at one time.
Plan on dropping about $20+ for 4 cupcakes and a bottle of something to drink. The cupcakes are okay, but I didn't find them amazing. They rotate flavors each day, so if you want a particular cupcake plan your visit around the day they are available.
I think a visit to the store is worth it just to say you did it. You might want to check out Sweet Lady Jane
for other pastries, but not cupcakes.