Rae, have fun with your OW dives!
I originally wasn't going to certify locally -- in fact, that was part of the bargain I made with my husband, that I would do the classroom portion of the class here and go to his dad's in Maui to do the dives. But I ended up certifying in Puget Sound in a dry suit. Here are a couple of tips: You should have a pool session in the dry suit before you go for OW dives in it. You will get a little wet in the pool, because of the exercises they have you do, but a little wet means maybe up to the elbows on your arms, and a little on your chest. If you have water standing in your boots at the end of the dive, insist that the seals do NOT fit. I did not know enough to do that, and it caused me a great deal of misery on the first diving day.
However, even in a couple of layers of my polarfleece stuff I use for riding in the winter, in a suit with fitting seals, I was able to stay quite comfortable for the short dives we did for the second day. I think you'll be surprised at how comfortable a dry suit can make you in cold water.
Come back and let us know how it went!