Yes, you need to clean the poop out as soon as possible. Would you want to crawl around in your feces? How unsanitary would that be??? :awcrap: If you leave the cage dirty, you are inviting bacteria to move in. This could make your snake sick. You should spot clean whenever your snake poops, then totally disinfect the cage at least every two weeks. I use Chlorhexidine to disinfect my cages, but I think most people use a diluted bleach solution (1 part bleach to 10 parts water, I believe). The reason I like to use Chlorhexidine is because I do not have to rinse it. The longer it stays in contact with the cage, the better it disinfects. It is not harmful to the snakes, so I simply spray the tanks, let it sit for about 10-15 minutes, then wipe it out.
As for a bath, it is not necessary. Some people put their snakes in the tub (lukewarm water) for exercise or to help with a bad shed. Not all snakes like it, though. It can be stressful to some.