I found the following worked for me:
# Check
find(:css, "#cityID[value="62"]").set(true)
# Uncheck
find(:css, "#cityID[value="62"]").set(false)
I found the following worked for me:
# Check
find(:css, "#cityID[value="62"]").set(true)
# Uncheck
find(:css, "#cityID[value="62"]").set(false)