Is it possible to travel one-way on international flights?

Unfortunately one way tickets cost almost the same as 2-way. You don't need a 2-way to go to mexico, you do need a pport and the tourist visa you get on the plane is good for 6 months. Then you either have to leave the country and come back in for another or get a FM3 which is a hle but allows you to stay for 1 year. If you need to get your tourist permit before you leave the US then you have to go to a mexican consulate. My guess is the cheapest flights are from LA, but there's nothing wrong with taking a bus.