C.,
I caught my son trying to climb out of his crib and was afraid he would break his neck, so I switched him to a regular twin size bed at 20 mos. I put one of the long sides and the top in a corner against the wall and a side rail on the open side that extended a little beyond half way down the length of the bed (so he wouldn't accidentlly roll out in his sleep).
The transition was easy, I just got rid of the crib and put the bed in the room. Occasionally, in the beginning, he would get out of bed and come out of the room, but it just took me being firm and consistent to convince him to stay in bed--if he got out of bed, I'd pick him up, tell him it was bedtime, and tuck him back in. He soon learned that I wsn't going to let him stay up, so he just stopped trying.
I did let him have some small, soft toys in the bed and sometimes would hear him moving around on the bed or playing a little bit, but he usually fell asleep after a while. Sometimes he would get up to play in his room. I didn't discourage this because I figured if he wasn't tired, he wasn't tired. But then when he'd fall asleep on the floor, I'd just lift him back into bed before I went to bed. Sometimes, actually often, he would wake up before I did in the morning and just play in his room or come in to wake me up. The tiny apartment was "baby-proofed" so it wouldn't have mattered much if he wandered around. One morning, I caught him in the pantry eating a cinnamon roll.
If the wandering around is not something you are comfortable with, you might consider the baby gate option, though if they wanted to, I guess they could climb it, so I'd make sure the house was secure and baby-proofed just in case.
As for child escape artists (my son was a mini Houdini), try putting a chain lock high up on the doors that lead to the outside. But even that will only work for a while. My son learned to grab the broom from beside the 'fridge and use the handle to slide the chain off (don't ask me how he figured that out because I have no idea). So you might want to lock up the broom too. ;)
Good luck. I'm sure it will go fine.