I am starting from scratch, so I have absolutely nothing in my portfolio.
Ah, then not only is it market timing, it's utterly pointless market timing. $5500, while it seems like a shitload of money now, is a tiny fraction of the amount you will be investing over your life. You could put it in the "right fund", put it in the "wrong fund", or, hell, even light it on fire (not recommended), and you wouldn't notice any difference in your life 30 years from now. However, you *will* notice a difference if you waste an hour trying to outguess the market every time over the next 15 years that you're making an investment.
Just invest in your desired asset allocation. No need to go 100% US stock this year. A Vanguard LifeStrategy or Target Retirement fund would be a closer match to your allocation than 100% US stock, or if you really don't care about bonds yet, Total World Stock will put you right on that 50:50 balance. Then next year when you have more than $6000 (or even sooner, if you can contribute to a 2014, or if your money grows as hoped!) you can divide into more funds to really dial in your allocation.