Luke Skywalker is certainly the most famous Jedi to work for the Rebellion, but he’s not the only one. Kanan Jarrus and his Padawan Ezra Bridger were involved in a variety of Rebel Alliance missions, as detailed in Star Wars: Rebels. They even were known to Princess Leia (Rebels: "A Princess on Lothal").
What’s more, former Jedi Ahsoka Tano served as the leader of the Rebellion’s spy network from shortly after the fall of the Empire to several years before the Battle of Yavin, and was certainly in regular comunication with Bail Organa.
Even C-3PO seemed to know something about Ezra, at least:
WHOOOOSH! Then brave rebels far away began spreading the word from planet to planet to fight back. And one boy sent a message across the worlds that ignited a spark of rebellion.
Beware the Power of the Dark Side!
If Leia and C-3PO both knew about Force-users (and indeed Jedi) who had worked for the Rebellion in the past, it seems possible that they might have told Luke.
Is there any evidence that Luke knew about these earlier Rebellion Jedi?