Stagger Traces in a Flex Circuit?
It is better to be alternating.

Why? this reduces the chance of I-beaming. If you refer to IPC-2223 "Sectional Design Standard for Flexible Printed Boards" 


  Conductors in double-sided circuits should not be placed directly
  over each other, which produces an ‘‘I’’ beam effect. This condition
  may be necessary due to electrical considerations; however, mechanical
  installation requirements must be considered (see Figure 5-5).




Also, traces on a flexi should be perpendicular to the bend so if those traces at 45deg occur at the point of bend, change the design