Can my washer drain do a 'u-turn'?
With plumbing it is all about maintaining the proper drop per foot.  The fact that this is a wash machine makes the call even easier.  I guess the theoretical issue would be would the 90s and slowing of the water make it more likely that something could stick to the inside bend and accumulate enough that you would have an issue.  My thoughts on this:


don't see what would stick to PVC from a wash machine
use long sweep 90s so you don't have sharp bends
and if this ever did fail you would have easy access to it