We are going to have a group of 10. Is there a limit as to the number of people you can have in a room or should we split?

Trust me, based on the size of the room, more than 10 would be to much. We had 10 and I found it was difficult to disseminate the information to and from everybody it was still fun though.

I think they accommodate 12 max per room. I havent been in a while but we only had to split into two groups and we have 20+ people

I think most of the rooms accommodate 10. You should check each room for its max. The rooms are designed so that the puzzles are solvable by about that many people within the time limit.

Good , don't need to split