Originally Posted by
nycphotography
Whatever you get you should get it soon so you have time to get used to it and to work out any fit issues before the big ride.
And at 5'10 you might consider a 54 frame w/ a longer stem and raised seat. I'm 6' and my 58cm fuji is maybe a half size too big (I had to shorten the stem). I should probably on a 56.
I agree with giving yourself time to get used to the fit. I have a Giant OCR C1 and it took me a looong time to get used to that geometry. Now I love it, but I tried 6 saddles, lots of saddle tweaking, different pedals and cleat positioning, and a shorter stem before I got it dialed in. And these things are interactive: change the cleat position and you may have to raise/lower the saddle or change the fore/aft position.
Btw, I'm 5'10" (long legs, short torso) and I got a medium Giant. They basically just have small, medium, large and maybe XL. I swapped the stock 90mm stem with a 70mm before it left the shop - or maybe it was 110 down to 90, can't remember.