Atl U.S. Open is on Eurosport but they don't have the number of red button screens as Sky do. I'm so glad we have Sky because it makes watching tennis so much easier but I know it is expensive but for us it is worth it. We're lucky I suppose.
I got caught in the Eurosport trap last year with the USO. Sky have a monopoly on Andy's matches and Eurosport don't show any of his matches live, so I paid for Eurosport Player for the USO and hardly used it. EP is great for the AO and the FO.
As you say, Sky is expensive, but I have other issues with it as well - this is probably not the place for that though!
I get frustrated by this every year.
I don't have Sky but I'm considering getting a Nowtv subscription for the second week (£10.99), which provides online streams for all Sky Sports channels.
I'm hoping that things could change next year - I think 2015 is the last year of Sky's rights to the USO. I did look into NowTV, but I just can't justify giving Sky/their owners any money!