If you have a place of your own where you can wash it, use a biodegradable non-toxic cleaning agent like Simple Green so that it doesn't foul up the sewer water more than it needs to. I pull the car up on the lawn so that the lawn gets watered at the same time, and when i can, will wash the car in the rain since I need to use much less water. Also, avoid washing your car when it's sunny as you won't need to constantly be hosing down the car due to drying times. For best results, get rid of your car...bikes have less surface area and are easier to clean.
Pros: Uses less water saving you money and if you wash in the rain, will make you a hit with the neighborhood kids.
Cons: Means you can't wash when you want all the time if you are waiting for the rain to come, and your car will most likely end up with water spots
