I'd switch to door 2.
To avoid confusion with the existing numbers, there's one door with a car behind it and another two hiding goats - call those goat doors X and Y.
There are 3 possible scenarios:
1. My first choice was the door which hides the car. When offered my second choice, I switch to another door (either X or Y) so I lose.
2. My first choice is door X which hides a goat. If when offered my second choice, I switch to door Y, I win (the host having exposed the other goat before offering me that second choice).
3. My first choice is door Y which hides a goat. The host is forced to open door Y and show me the other goat. If I switch when offered my second choice, I win the car.
In the first of those scenarios, I lose, but in either of the other two I win, so the odds are 2 to 3.
If I don't switch when offered my second choice, then:
1. I win - I choose the right door first time, and stick with it.
2. I lose - I choose door X first time round and stick with it, but it hides a goat.
3. I lose - I choose door Y first time round and stick with it, but it hides a goat.
In the first of those scenarios I win, but in either of the other two I lose, so the odds are only 1 in 3 when I stick with my original choice.
QED (I think!)
Andy