Also consider the Air National Guard and Air Force Reserve. These branches actually hire new pilots off the street and send them to AF flight training.

You already have a flight slot (and an aircraft assignment) before you start training. Additionally you can pursue an airline career in parallel with reserve service, so you can get a better airline seniority number. Most ex-military airline folks would say the this route is best if you intend on doing airlines.

Like others have said you might still be able to do ROTC (only during undergraduate, not post-graduate I believe) and might even be able to get a 2-year scholarship. But you could also be assigned to a non-aviation job out of ROTC. With the guard/reserves or going regular AD through OTS at least you could get a guaranteed flight slot before you commit yourself.