Oh man. I had this same problem in my 93 Eclipse. I took it in for repair and essentially the guy rammed a rod down the hose and cleaned it out. Stayed that way for a summer and then wham - again. I finally got rid of Mr. Mold. Great car other than that.
If you're going to keep this car, I would find someone that can truly repair it because mold eventually becomes a hazard if you don't do a through clean up. Of course, mine would save up and then dump a bucket of the cold cold water on my feet when I took a turn. Your problem may not be that bad yet. Do tend to getting the water cleaned up and dried pronto though (rather difficult if you run the a/c though).
I will say this, cleaning out the drain hose that is currently there is not a big deal. I would try to find someone that can figure out how to actually fix it. I don't know what it clogs with, but I have my suspicions and have to say "yuck". You might also check and see if there's not some recall on this too. I can't imagine that this would still be going on with no fix by Mitsu!
p.s., Personally, I would not try to clean this out myself (with a rod) in case of drain tube rupture. It's inexpensive to take it somewhere and have someone else take the responsibility.