We were in F. No changing table in the F lav or the lavs in the back. The very apologetic crew confirmed some MD-90 and some 757's don't have any changing tables. I just assumed every plane had at least one.

To summarize the options (none good): don't change the diaper, change at your seat, or change in the lav on the toilet. The first two smell up the cabin, the last is unhygienic and potentially dangerous.