divediva, I'm arriving in approx 2 weeks as well and plan to do a lot of diving. Gaz and I have just been discussing the water temps. Normally they'd be around 81F, give or take a degree. But there have been continuous Northers for the past 2-3 months and the water temp dropped considerably.
The good news (for you and I, at any rate) is that the water temp is rising again at this time. It's now around 77F, according to Gaz. That's still a bit chilly to me in my full 3mm. I'll need a hood for that and probably wouldn't mind a 5 mil on my core.
Even when the water temp is 81F, I wear a 3 mm and can get chilled after a few days of dedicated diving, but that's me. Everyone is different, what are you used to? What's the norm for you? Do you usually do many dives over many days and at what water temp? What protection do you usually wear under those circumstances?
The point I'm trying to make here, is that while I need a full 3 mm in 81F water, some people like Axeman are fine in a shorty.