A good quality electric fence system within a field with properly constructed pig netting and barbed wire will keep the pigs in. Two strands of galvanised wire with wooden posts at the corners and plastic posts at two or three metres seems fine for all our Saddlebacks (famous last words). We now have to coax them to cross 'the line' when we take it down. Young pigs will panic a bit the first time they meet an electric fence, but don't panic, round them up and put them back. They should get the idea in a couple of hours.
If in doubt, get someone who knows what they're doing to help and don't skimp - it's worth laying out some cash on good fencing. Pigs will escape through a bodged up fence. Plus, we've found they're less likely to try to get out if they've got plenty of space, so give them as much as you can/dare. And run the electric fence off the mains if you can, but brand new 12v batteries if not (again, don't skimp).
I don't think it matters what breed you go for and crosses can provide better meat. We have Saddlebacks so we like them, but we had a couple of Tamworth crosses who were great and provided two very big carcasses at nine months. In future we'll slaughter at around 7 months as you can spend a lot of money on a lot of fat as they get older.
Hope it goes well. Pigs are terrific animals and I know you'll have fun with them.