Re: U.S. Open
There are probably some in Koreatown but it's a bit of a walk. I certainly wouldn't bother and there is enough variety at the Food COurt that you can get something other then a hamburger for $12. And bottled water is only $5 and better for you.
I usually throw some peanut butter crackers in my bag or breakfast bars and so only get something late in the afternoon like a big salad before the night session crowd comes and it gets really crowded there.
You can bribe an usher in Ashe but it will cost you $50-100 depending on how low you want to go and at least for me the lowest I've ever gotten was right above the upper lux boxes. In Louie there is no need to. Only the first 10 rows or so (I believe) on one side of the court are reserved seats. The rest of the Louie is first come first serve.