Can we access the developer menus in Prison Architect?

Update for version 2

As of version two this is now possible! When creating a new prison you need to check the box marked "Enable cheats". This:

• Makes all construction instantaneous
• Adds a "spawn" menu that allows you to place anything for free
• Allows you to speed up research by holding the right mouse button down on the icon
• Allows you to place water

More useful for developers (excluding F11, which has general use) are the function keys:

• F1 Edit world properties (Very easy to crash/ruin the game)
• F2 Profiler
• F3 Script Debugger
• F4 Dialog Editor
• F5 Sound Editor
• F6 Sprite Bank Editor for Needs icons
• F7 Sprite Bank Editor for User Interface icons
• F8 Sprite Bank Editor for Game Sprites
• F9 Debug rendering options
• F11 Enlarge Map in All Directions

For prisons without cheat mode enabled

For prisons created before V2 or created with cheats disabled, modders have been hard at work creating their own similar system. This can be installed through the steam workshop.

Update 2017-03-17

This is now possible. See Rory's answer.

Old answer:

Currently, the answer is "no". Introversion does not include debug features, such as the indeed nifty debug menu as seen in multiple alpha videos, in their alpha releases. Whether they might do so in the future at some point, no one really knows, as they haven't said anything about the debug features at all in any post whatsoever (as far as I've found).