Can I uninstall my Steam games but still have the save?
Solution 1:
Some games will keep your save data in a separate folder such as your documents folder on your computer, which means you shouldn't lose the data in those cases when you uninstall.
I also believe the Steam Cloud feature sure work on most titles in terms of keeping your save data.
But as Ben said it's always recommended to manually find the save yourself and copy it just to be safe.