Not sure about the discount. But I always park in the parking garage or the lot directly across from market. It can be accessed via Prince St. There are also side streets you can park on on you don't mind walking a few blocks.
We always park at the Prince street garage. $2 for the first hour
There Are Several Parking Garages And Plenty Of Street Parking Near The Market Just Depends If Your Ok With Walking
I don't recall the location of the garage we parked in last month, but it was about 1-2 blocks from the market. Walking gave us the opportunity to see other things since it has been a few years since my last visit to Lancaster.
No discount from the market.
There is a free lot across the street. Also the indoor multilevel garage is a couple of blocks away. I don't know of a discount but it is not expensive. Visit all of the venues on the way to the market. Fun walking.
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