Thanks go to Wondermike for bringing the excellant post by sixspeed over to this site. Cleaning the drain plugs should be a part of regular maintenance. I discovered a Q&D (Quick and Dirty) way to do it.
Take a good look at the sixspeed pics and get a sense of where those drains are and also read his text. The passenger side is the easier to work with. I took a wooden pole, used for marking driveways in snow ($1.00 at Home Depot), and poked around until i found an opening. I reamed the hole and a flood of water came out with some other junk. I was amazed. I was content with that. I never took off the splash panel on that side (I told you this was Q&D).
The driver's side is different - the hole is not accessible from the top. But, it is no big deal to take that rear wheel forward splash panel off. I did it without removing the wheel nor did I jack the car up. Two 8mm nuts and a (plastic!) 10mm nut are visible. It is a tight fit back in there, but you can get it done. Then there is the 8mm bolt/screw back behind and below the mudflap. The mudflap is separate from the splash panel. That last 8mm bolt/screw is easy to see if you take a mirror under the car. Wiggle the splash guard and you can approximate where the bolt has to be.
With the panel off, use a flashlight to peer back and you'll see the black rubber plug. Yank it out. Take a flexible tube or wire to whisk out the drain hole. There was nothing coming out on my car. So, I put everything back.
Should take you 20 minutes the first time you do it, depending on how much time you fiddle around trying to find tools small enough to fit in the driver's side wheel well. I have a small 1/4" ratchet set that worked well. Ideal for that 8mm bolt/screw behind the mudflap is one of those 8mm-9mm-10mm "Y" wrenches sold at bicycle shops.