One of my squad leaders is about to PCS back to the states to Ft Bragg for SFAS.  He's been doing his own PT with a ton of rucking.  He did a 10 miler today; ran it about half the time.  
A lot of guys will enlist and think they're hard enough for SF, but realize they just aren't cut out for it and get sent to infantry for five years with a shitty bonus or none at all.  If you're dead set on being an operator, I would enlist infantry (get a good bonus), do a combat tour, and then go to SFAS. 
And, ya, we might not be in Iraq for much longer.  But we'll be in Afghanistan.  You'll get better experience there anyway.