If all you are doing is testing the map to make sure the ladder or other minor additions are working properly, you can simply do the BSP_bsp phase of the compile (The first step in MBuilder)
You can then copy the .bsp file it makes into your dm folder, and start the game normally to test your map.
You will have an overbright map since no lighting is done, and you will also not get accurate (or very good) framerates since your vis is not done.
But it is a good way to test your map for the rendering and function of brushes without having to completely compile it.