I have 32x11.5 50R15 tires on my 86 Samurai. What is the proper inflation pressure for on road and off road use?

Basing what pressure to run by what the max pressure rating is, is not at all correct.  Max pressure rating on a tire has absolutely nothing to do with what pressure you should run.  It has to do with a combination of things like......weight, desired ride, desired tire wear, desired MPG, etc.
There has been some recent discussion on tire pressures on here.  Do a search or look through some of the threads from the last month or so.....there is a lot of good info in those threads.

The max rating on the tires is 50 PSI. I would need a bite guard to prevent the fillings in my teeth from vibrating loose driving with 50 PSI in the tires. LOL. Given the Samurai weighs so little, I'm guessing the highway pressure on those large tires is going to be low  (maybe 20PSI?) but I really don't know. I did search here and at another Suzuki forum before posting but didn't find an answer.

23 or so is what the sticker on the door says for tire pressure.  Some people run that, some people run more, some people run less.....it is just a matter of preference.  Personally, I run 30 in all my samurais and sidekicks, when I drive them on the road.....that pressure offers a good compromise between everything I listed in my other post.  My offroad pressure varies between 5 and 10....depending on the tires, the terrain, and the samurai.

I have 33x12.5 on my SJ, I usually run 25 on the road and 12 on the trail and 6-8 on rocks with Procomp Extreme MTR's.  With my previous tires, 33x12.5 BFG MTR's, I ran 15 on the trail and 8-10 on rocks.  25 for the road.