E.,
Since he's climbing out, that MAY be part of the thrill. Maybe you can switch him to a toddler bed. We did this for our son about 3 months ago (he was about 27 months). He never climbed out, but we just felt it was time.
The first night was great, but then he realized his freedom. So, what we did is put him in bed and tell him that he needs to stay in bed. I'd close the door, but leave it open a tiny crack so I could peek in. I'd watch him and if he got out, I'd go in the room, scoop him up and put him in bed. No eye contact, no talking, nothing. After about 10 times, he realized it really wasn't getting him anywhere and he fell asleep. This went on for about 3 nights and he finally gave up. Now he won't get out of bed until the morning or after nap.
There were times that he thought it was a game and would laugh or say "Hiiiiiii" when we came in the room. We didn't respond to anything he did. Just picked him up and put him in bed. Both my husband and I did this (in shifts since we had a newborn, too) so he knew he wasn't going to get away with it from either of us.
Good luck.
T.