As far as when to plant it depends on what your latitude and region is... May is correct, but it's standard that 4/20 is planting day in most farming regions...
-Your planting area.
You will want to make your hole a whole lot bigger than that...
I suggest digging around a 4 ft circle, and digging as deep into the clay as you can, 3-4 ft deep... The clay is terrible for roots, they hate it. You can backfill with topsoil from around the area, the top foot of black soil.
- Advanced Nutrients makes a time release fertilizer I've used on tomatoes and pumpkins, there are three applications, Spring-Summer-Fall, they are granules you sprinkle on top of the soil. I had amazing results.
An hour hike seems like a lot of walking to be bringing serious tools, so bring some to leave there stored under some black plastic and some branches...
Also since it's such a long hike, maybe look for multiple sites to put a few plants, animals and people might stumble upon a site, but the others will still be alright.
When harvest day comes, trim off as many fans as possible, you can just snap them with your hands... Stack the plants on some black plastic, wrap them up, tie some string around it, and stack them near where you'll load up a truck, hopefully it's not a busy, or heavilly patrolled road, or you'll have to find another way of carrying shitloads of weed... Many, many trips with big backpacks.
Think these plants are going to be 13 feet tall, there's going to be a lot of buds.
I filled a entire shed with my first grow of only 12 plants, they were monsters. I didn't have the knowledge I do now, so I can't wait to start growing outside again, growing indoors is SOOOO much work, and SOOOO expensive. I've been doing it inside for 6 years now, and want to go back to outdoor growing...