hey, sleeping in your car is not the worst idea. the previous post about the FREEZING conditions should be considered though. but if u have a dozen down blankets with you...then you should park along a nice looking residential street without parking restrictions such as required permits, no overnight parking, street sweeping, etc. It is usually better to park between two houses or along the side, rather than directly in front of a house. or parking curbside along a quiet street in front of some fancy apartment buildings is not a bad idea either. the idea is to tuck in between some cars and keep low.
there won't be a problem if you park at ur chosen location after sunset and leave before sunrise. you won't need more sleep than that!