Vertical against a wall

I'm brand new to SFG and just built my boxes for planting. The only area in our yard which was available is against a 4-5 ft brick wall. It's on the east end of our yard and the house is a 20-25 ft away, so against the wall, it gets sunlight from about 12 to 8. We want several things to grow vertically (for growing squash and sugar snap peas, maybe a melon), so I'm trying to figure out trellis options. The wall is a retaining wall with dirt up to the top on the other side.

1) I thought of stringing some trellis netting along a piece of conduit and then staking it into the dirt on the other side, thus holding the netting the netting in place up the wall. Do I need some additional framework to support it?
2) I went to HD and couldn't find any netting, so I had another idea--just build or buy a wooden trellis ($13 at HD) to stake against the wall. Do I still have to run netting or can I just train the vines along trellis (about 1 foot square gaps)?
3) Is it a problem to grow these against a wall like this?
4) Can I plant these larger plants (that take up 2 squares) next to each other (in adjacent squares running perpendicular to the wall and not along it)?

Hi JeffandChelsea... welcome to Square Foot Gardening! I'm a newbie to gardening, and the people here have been a wonderful help!

To address your situation, first, I think the brick wall you're using will retain heat, so that's something to keep in consideration. If you have warm days and cool nights, it will have a tendency to balance the temperature differential, so I'd think it's a good thing.

The pre-built wood or metal trellises should do just fine, unless your vines get REALLY big. Some vines (squash and cucumber, for example) can get to be 10-12 feet long, but they probably can be trained to go back down the trellis if need be.

Good luck and happy gardening!