Setting up rates is a tradeoff between performance and range. Realistically however turning of 1, 2 5.5 and 6 is always a good idea unless you have a very sparse deployment - in dense networks we recommend turning off everything up to 18Mbps One other tip for macbooks is that you should enable WPA-AES and avoid WPA Auto, macbooks tend to prefer AES.
By the way, I realized that I didn't answer your 5GHz question, Three things there:
+You may turn off the low rates in 5GHz as well however you don't gain as much
+If you want to encourage clients to move to 5GHz you can turn on band steering
+Finally, make sure you utilize 40MHz channels.