You should play in the U1800 section instead. There are enough sandbaggers that you don't stand a chance of winning money, so you may as well play for experience against stronger opposition.
World Open

Thanks for the encouragement, Fromper. However, I did not ask about what section to play in (too late now). I want to know how to prepare. What should I do in the upcoming months???

At 1599 USCF rating? Lots and lots of tactics puzzles. And read Silman's Complete Endgame Course. And play a lot, and analyze your games, preferably with stronger players.
The usual.
And actually, it's not too late to change sections, just because you pre-registered. They'll usually let you change up to an hour or two before the tournament begins.
yeah.. because of sandbaggers there is no point playing for money.. unless you are one.. that's why i always play in open even my uscf is 1950 .. you always can beat up on some old master and get your rating up plus it feels good
Practice tactics couple weeks before tournament.. review openings you play... rest couple days (no chess) before tournament.. it's a long tourney
P.S. keep eyes open for cheaters
How should I best prepare for the World Open. I am rated 1599 (no, I didn't sandbag), and will play in the u1600 section.