We actually drove within 300 metres of the address (as the crow flies) while going west on Beltway 8. (Twice, in fact — once on our way out of the airport and again on the way to Katy Mills.) But we didn't necessarily know this at the time; it was probably just after we got back from Katy when I looked it up.
We never got around to getting a stamp to post it in Houston, and to our surprise there didn't seem to be postal facilities of any kind at the airport where we had a couple of hours to kill before flying back home.
So it had a free ride back on the plane and now it's back to plan A.