The drain hole is a little hard to find. It is on the firewall and on my car it is directly above the front of the main cat. It does not have a "duckbill" flap like many cars, instead it is just a hole through the firewall into the A/C plenum. If it is plugged, you should be able to clear it with a bent coat hanger.
As Rob Shaw posted, it is very likely that your cabin filter is dirty. If you have not changed in the last 12 months, you should. That can be the source of your odor. Thaere is a great FAQ on how to change it.
