Yeah, there is no (yet) ledge grabing on ut2k4, what the bot did and you can do is double jump (obvious), wall jump (jump moving towards the wall and when near to wall double click move button [opposite of the wall], and you'll dodge off the wall)
Also if there is a piece of wood or something put near the wall you can dodge onto it and then double jump, by using this technique you can save a lot of time moving around the map, and save a lot of health.
I used to play in 3rd person view (default F4) in single player with no bots to learn dodging tricks. It helped me.
hood luck