* Auto-lock after driving a certain speed: This feature locks the doors automatically once the car reaches a certain speed (usually around 10-15 mph). To disable this, you'll likely need to adjust the settings within the car's computer system. Unfortunately, the 2000 Avalon likely doesn't have this easily adjustable through a menu in the car. It's highly probable this function is factory-set and not user-configurable.
* Auto-lock when the car is turned off: This feature locks the doors automatically once the ignition is turned off and the car is shifted into Park. This also cannot be disabled on a 2000 Avalon through a simple button or setting. Again, it's likely hardwired into the car's electrical system.
In short: For a 2000 Avalon, completely disabling the automatic door locking is very difficult, if not impossible, without potentially modifying the car's wiring system (which is strongly discouraged unless you have significant automotive electrical experience). You might be able to find aftermarket solutions, but it's unlikely there's a factory option to simply turn it off. You'll likely have to manually lock and unlock the doors yourself.
