Hm, well circling an area ONCE by boat is a real life marine act for "burial at sea" based off of traditions from the British Navy during the great age of piracy (or was it twice? I don't remember off the top of my head). I don't know which translation everyone read, but the one I saw never mentioned circling 3 times.
Also, on the note of Luffy's tatoo, I couldn't make it out well enough to know for sure that it said SA2Y or whatever the theory is, so we probably shouldn't jump to conclusions. Besides, whose to say that the picture shown to us was the ONLY picture to show up in the newspaper? There might very well be one that has a full shot of the tatoo.
I still think the key is in the 16 bells though, since ringing it 2 times marks disaster (which is what Luffy would have done if it was only to mourn the losses) so ringing it 16 times means something else. I don't agree with the new year theory, since there's no indication that all the crew members would catch the significance. Like mentioned, Kidd didn't even know until Killer explained.
All in all though, I'm sure Oda will come up with an acceptable explanation and I'll be smacking my head going "Duh! I should've seen that!"
EDIT:: Alternatively, it could be some information that most characters of the time would know of (like some sort of tradition for sailors) that won't be revealed to us until later.
Another thing I noticed, while I agree it probably doesn't refer to a place, it might not refer to a time either. Remember that Luffy has no idea where his crew is. So the whole 16 days of weeks or whatever might very well not be enough time to get to where they're meeting. Keep in mind it took Roger 3 years to conquer the Grand Line. The passage of time might not be clear in Luffy's adventure, but traveling the Grand Line takes a significant amount of time under normal circumstances. Although, one of my long standing theories is that Luffy will beat Roger's record, so who knows, I could just be rendering my own point moot XD
However, outside of a time or place, I can't think of any other significance the message could have, so I may very well be wrong.