Street fair is fun. Go hungry and thirsty and with lots of small bills. Helps to have a friend with the same tastes as you so you can split lot's of stuff. If you find a place to sit - do not get up!
or do and don't plan on sitting again. If you drink beer - get it from the liquor store. MUCH cheaper then your other choices and you'll get an actual beer's worth. Not a cup's worth. yes. you'll still have to pour it into a cup but you'll get more.
Paying for parking is worth it if you plan on spending all darn day there. You'll be full and tired upon leaving and do you really want to walk several blocks into the neighborhood to get the car? Mmmmm... street faire....