That could cost a fortune - there's no good way to get to Farmer's Market that I know of from DL. Maybe check the metro lines? If you can take a bus or shuttle to the metro I'm sure one of them goes to Farmer's Market.
Is there something really compelling you to go there? It's interesting but not worth spending a ton of time/money to get to imho (well, unless you've got an American-Girl obsessed daughter maybe)