You never know what you will get in hurricane season in the Caribbean. The first year I booked TTR it was for around October 7th, and I ended up changing my dates to join the Chaos Crew (2011). Apparently a tropical depression or some such nonsense blew into Cancun the October week I had booked and the ground floor rooms at TTR were flooded. Eeep! Insurance is probably a good idea if you plan a trip during hurricane season. I've heard that odds are low of bad weather by the time you get to the end of October...hurricane season has pretty much wound down. I've never heard of any sort of regular groups in September. I've been at TR around Labour Day and there are regulars that go then, but that's just thru til Labour Day or a couple of days after that.
We went last September 25th to 9th October.. It did rain alot but didn't put a dampener on our time there. If the rain came down at night they moved the entertainment to the sports bar, which we preferred. Must say we went the year before to another hotel and it didn't rain once, so guess its pretty much hit and miss. Oh we've booked up again for this coming September for the same dates.