I have a Lexmark S600 that says WiFi in the front. Can I print from my IPAD?

You will need a third party app. Your printer is not AirPrint compatible. You can check here if you like.

http://support.apple.com/kb/ht4356

There are apps available that allow you to print with virtually any WiFi printer like Print Central, Print and Share and others. There are apps that let you use your computer as a server for your printer. Printopia for the Mac and Print Magic for Windows are two such apps.

I like the server approach mentioned. Just works better than the apps I've tried. FingerPrint works well for PC. I couldn't get Print Magic to work.

Lexmark also has an app so you might want to look into that as another option. No idea if it's good or not, just seen it mentioned.