I would say the opposite. College is awesome. You could do it anytime but the best time to go through university or a college is now, while you are young. On the other hand Silicon Valley is not going anywhere. If you are talented, there is a place for you in the valley anytime you want.

The Economy is cyclical. The best time to grow is during a bubble. In a couple of years when all those me too incubators have burned themselves up there will be fewer people willing to tunnel him into the US... He could do his Graduation during a bust.

If you think a company will be able to sponsor his H1B without him having a degree (usually technical) then think again.

Have you actively contacted companies you're interested in and asked for interviews? It's much harder to wait for someone to contact you than it is to send a personalized e-mail / resume to each company you're interested in.

I'm also a tad worried that you skipped the portion of my post regarding looking for pure graphic designers. It may just be my experience from companies I've been in but the last two graphic designers I helped hire were combo packages.

It's nice to see another 19 year old excited about startups and technology though :)