"Brush up on Swedish???"
You will do fine with English, but older people (especially in rural areas) aren't as good with English as younger people are. I am not fluent in Swedish, although I know a few phrases for politeness: please, thank you, hi, goodbye, etc. and I can read much more than that, and I was able to get by with mostly English on my trip a couple years ago. (I never made it to Grava, however.)
It does help to learn some food words. ;-) If you eat in a restaurant all the time, you won't need those words because the servers should speak English, but if there is an outdoor booth, foods are usually listed in Swedish. The vendors probably speak English but it is nice to know what you are ordering when the lines are long.