I don't have any of my machines on MS accounts. There really isn't a need to.
The issue with free WiFi isn't because of the possibility of malware. It's because open WiFi (that which does not require a key) is not encrypted and can easily be sniffed by other not-so-nice patrons using the same free WiFi.
All you passwords for things like social networking, your email, etc. may be able to be viewed in clear text. Just because a site uses HTTPS at the beginning doesn't mean they use it once you are logged in. Many sites don't.
Add a web filtering tool to your laptop to filter out known malware and phishing sites.
http://www1.k9webprotection.com/