I just got my poster-sized print back from Staples and I'm really pleased with the results. I didn't expect much resolution from the Facebook copies of pictures, but was pleasantly surprised. I went to the albums, and opened one picture at a time, then dragged to a desktop file. I think this eliminates copying low-res thumbnails. Here's the detail:
230 pictures
24" X 18"
set picture size to 500 pixels
Final cost $19.20 with tax The faint watermark in lower corner is not worth paying $25 for pro version of the free software