I am interested in buying Office for Mac 2011. I am in Sweden. Whenever I want to buy it from a website it shows like Office för Mac Hem och Student 2011 - 1 Paket (Svenska). Does it means software language is Swedish? I want it in English, as I am not Swedish. And my MacBook Pro (OS X Lion) language is English. Should I buy this one?
This is not a problem. What matters is the serial.
The same serial should work with any language version of Office Mac 2011 which you can download from Microsoft's official websites.
I had a similar problem like you. I had purchased an English version via Ebay, but I needed a German one. I downloaded the German version and used it with and US version serial without any problems.
In your case you can download the US version here: www.microsoft.com/mac/downloads
Have you tried buying the US English version directly from Microsoft's website (link)? It's a download (no disc).