Not sure what term you're in but startups - particularly the smaller 2/3 team ones, can't absorb more junior developers. But if you're in 3A and above you should be strong enough to hit the ground running.
There's also immigration issues. To get a J-1 visa the host company needs to meet certain requirements.
In any event as a Waterloo alum currently doing a YC-backed startup in SF, we'll be posting jobs in the next co-op round.
