I wouldnt try it........are you talking BUS??? rental car? taxi? private car?
forget the bus...and forget the rental car( it takes too long to pay them off , they are slow as molasses)...A private car you can pay right before you get to the Airport.....but you have to pre check your bags, then go through check in.... then go through immigrations and xrays....
I am sure there is a minimum time you need to check your bags...I bet at least 30 minutes before the plane leaves.......maybe 45 minutes.
if there are flights after yours you can get caught up in that mess......I really think 2.5 hours from POP to take off at STI....is too little time.....
I have made the trip over the mountains in about 1:20 minutes a few times...but no one held me up...and i passed a lot of cars.
call hillbillys friend and ask them the minumum amount of time they would suggest for that trip....they do it for a living.
bob