Kehilat Yedidya is located on 12 Nachum Lifshitz Street in Baka, Jerusalem. Nachum Lifshitz is a small street, rather hidden in the Baka neighborhood of Jerusalem.
If coming from the center of town, pass "Gan Hapa'amon" -- the Liberty Bell Park -- always bearing to the right onto Rehov Emek Refaim. Follow Emek Refaim to its intersection with Pierre Koenig and Elazar Hamodai (second traffic light). Turn left, cross the railroad tracks, and then turn left again almost immediately (at the first traffic light, next to the gas station) onto Rehov Yehuda. Going up Rehov Yehuda, pass Rehov Naftali on the left, and then turn right onto a small street, Rehov Gad (at the Efrata School, the former home of the Kehilla). Take Gad until you cannot continue any farther (~2 blocks) and turn right onto Rehov Lifshitz. Kehillat Yedidya is at Lifshitz 12, about a block down on the right side (and a bit after another bet knesset on the same side of the street).
Rehov Lifshitz is a small street with limited parking, if you are coming by car you may find it more convenient to park on Rehov Gad, and to walk down to the shul.
Want a map? Go here, enter "Jerusalem" for city, "Nakhum Lifshitz" for street (you have to spell it exactly that way), 12 for house number, and hit Find. It will also give you directions from any address, assuming you spell the street the way it wants you to (hint: if you can't figure out how to spell your street, try the name of a nearby street - I couldn't figure out how they spelled the name of our street so I entered "Gad"). They have a service that would let us put a direct link to the map, but it costs $245 a month.