If they are parked next to your property and you have sprinklers, change the 1/2 circle to a full circle, and their car will be washed whenever you turn on the sprinklers, causing water spots.
If you are able to back in to your driveway, it would be a lot easier getting out. This may not be an option, and I really sympathize with you - miserable neighbors are awful.
Every time you need to leave, knock on their door and ask them to move their vehicles. If they become a problem when you make the request, call the authorities or your mayor. Sounds like it's an access issue and when the houses were built, the city should have prevented that.
As someone mentioned, squeaky wheels get the grease.
......You look like I need a drink.....