options->Configure->List Column Section->Options
Set the Work Effort Unit of Measure to "% Availability"
Hit Save
Allocation and Allocation By Period will now be in percent.
if you want to see the % sign then go into Options->Configure->List Column Section->Fields
Select the Allocations property icon, and set the "Display Type" to "Percent"
Save and Return,
Please note you cannot make the Allocation By period display the Percent sing in the same way.