Definitely not straight into the creek! At least not before you call you municipal authority's Environmental Health Services or an official performing the function and have their written permission (which they are unlikely to provide). These are the people you'd go for a well permit to. You might have already dealt with them if you dropped off water samples for pool water quality testing.
There are some nasty chemicals among the sanitizers (bromine, chlorine, cyanuric acid) and they could be in quite a high concentration. Normally you're not supposed to drain it into a body of water (lake, stream, wetland). It is also recommended that you stop adding sanitizers a week or more before draining to reduce the chlorine level. If the acid and chlorine levels are low, you may be able to use the drainage as an opportunity to water your lawn very well. Â
There's another side to completely draining the pool and that's a potential damage to the pool caused by ground water pressure from beneath the shell, what is described as "popping out". If you've never done it before, I would strongly recommend to have a professional pool company do it for you, and take notice of steps they've taken in case you need to repeat the process.
This question has been discussed in the forums. Check out this interesting thread for more suggestions (and warnings!) on draining a pool:
formatting link