Swedes speak very good english, although thats about all the english you'll see on the streets of Gothenburg. No signs or any information in gothenburg is translated into english, so it's not very tourist friendly in that way.
It might be a good idea to learn some basic words, but swedish is pretty similar to english, it's not hard!
But everyone under the age of 70 speaks pretty good english in sweden, so just ask us! We're friendly :) Many speak good german, spanish and french.