So i know messengers ride rain or shine, and most races happen that way as well. And you have your rain gear, and your fenders....but when it comes down to it...is riding in the rain safe for your bike? I know alot of fixies don't even have spots to drain in the bottom brackets. Does a simple wipe down keep you worry free or are there other precautions you should take?
Boegaard or framesaver is your friend. When installing seatpost and stem, make sure to use liberal amounts of grease so as to create a grease-barrier to stop water from getting into the tubes. Car wax will help protect the paint. Make sure to wipedown at the end of the day, and if possible, remove the stem and seatpost after a heavy rain day.
Sure, a hole might make it easier for stuff to get up in your BB... on the other hand, where's that stuff coming from? The crap from the front wheel should be mostly settled by then. And with a sealed BB, you don't really have to worry at all because the stuff that gets up there isn't really getting in, but that water will do some damage to your frame and quite possibly the BB as well.
Bottom bracket drainage holes are pretty standard practice and if you look around, you'll see a lot of frame come with them stock.