After. There is always the chance that if the signal running into the effect doesn't have the low frequency content, the effect may create it. It's safer to go after.
always after for me, IF i am looking to clean the reverb return up and not muddy my mix up.
putting a HPF before the reverb would simply just be sending a sound with less low-end, as opposed to after, which filters any low-end build-up the reverb may be creating...