How many other applicants are in the same boat?
I would personally recommend picking up some Python and maybe Pylons and start hacking some webapps (others might recommend Ruby and Rails, etc). How else are you going to build a demo from the 15k that YC provides?
it's pretty serendipitous that we stumbled upon YC about 4 days before the application deadline :)
we're working with a family friend who has had quite a bit of success in the SV startup world, and he seems fairly convinced he can introduce us to a friend who can do some work for us as a favor, and a perhaps a bit of money or equity (certainly not founder status).
furthermore, our concept doesn't really require any intense programming in the first iterations. it won't be until we actually prove the concept (via a barebones site) that we will need 'heavy hitters' to take things further, and by that time we feel like we will have acquired at least some funding based upon how well things have been progressing thus far.
best of luck to you as well :)
Understanding PHP/MySQL is nice because it allows me to communicate with hackers, but I wouldn't know where to start with anything serious like writing an API.
FWIW, I'm not a hacker, either. UX, XHTML, CSS, JS, SEO and other assorted acronyms are my bailiwick (though I can dork around a bit with rails/PHP/etc). Of course, I've also dabbled in accounting, sales, etc.
In my experience, a solid designer can easier keep pace with 2-3 coders (it's just that much harder to code something than it is to design it)... Which means (in my book), that a non-coder had better be prepared to do other stuff in the early phase of the project (notably SEO, SMM, and public relations).
(by the way, checked out your portfolio-- nice design work!)