I was simply offering my input based on the Star Wars NOVELS.
Specifically "I Jedi" goes into depth about how and why astromechs have ROUTINE memory wipes. Luke's R2 unit avoids this over the years ONLY because of Luke's sentimental attachment to the little droid.
As for C-3PO, Uncle Owen wanted to have his memory wiped. Why would he do that unless he knew that the droid would MAINTAIN his ability to understand the "bianary language of moisture vaporators" and still speak "Botchie". It was obvious WAY BACK THEN that memory wipes were a common occurance. IMO
Did R2 know where he was going? Probably, after all, he does have built in sensor, even if his own range is a bit limited. Still, the info could have been provided by Princess Leia.