Yes, this probably is the best place to ask.
 
Not because of any special knowledge, but because this site is small enough that the Admin actually will answer, and you are somewhat safe from belittlement, or non-answers from 10000 newbies that know far less than you.
 
I don't really have a "magic bullet" answer, but here is some general thoughts that may help you:
 
1.  Android is Linux, and can be a fairly full Linux -- including external keyboards, HD's, Ethernet adapters, mice, etc.  There are near-desktop functionality apps for Android, and many more apps than are available as packages for any given Linux Distro.
 
Access to a terminal, and most linux commands (through busybox) is easy.  Linux command line stuff compiled for the processor in your Android device (arm) generally work, and can be found on the 'Net.  Root access is possible on pretty much any Android device.
 
2.  There are full Linux distributions (Usually Ubuntu) for some Android Tablets and some phones, but don't expect full phone functionality on any device/distro I am aware of.
 
One example of a working Ubuntu for the Viewsonic G-Tablet:
My Review of the Device (running CyanogenMod Android): http://linuxslate.com/Review_Viewsonic_G-Tablet_Android_Tablet.html
 
Working Ubuntu for this device: http://forum.xda-developers.com/showthread.php?t=894960
 
3.  CyanogenMod is a community Android for many devices.  It is functional, customizable and stable.  Here is a list of Devices with official CyanogenMod firmwares:
http://www.cyanogenmod.com/devices
 
Notice that there are phones and tablets.  Phones (generally) retain full phone functionality.
 
4.  Some 3G-enabled 5 inch and 7 inch Android tablets have Phone functionality.  Chinese ones, while perhaps not of the build quality of more main-stream devices, may actually offer more in terms of I/O ports, and hacker-friendlyness.
 
Here's a search that will return some example examples:
http://dx.com/s/7++android+tablet+phone
 
Note that I am recommending any of these devices, and as you can read on the main Linuxslate.com site such Chinese devices often have severe usability issues.   I'm just showing that such devices exist.
 
Seeing that they are often not a significant expenditure of funds, I would not hesitate to try one of these off-brand/no-brand devices if I were in the market for such a device.  Look carefully at the specifications, and try to judge quality from the pictures as best as you can.
 
Post back if you are interested, and I can tell you some specifics to look for when reading the specifications.  Some things you may think would be show stoppers, may not actually be so bad, and similarly some things listed as "features" may be better interpreted as warnings.
 
You will never know much about the OS until you get the device in your hands, and OS updates almost never happen.
 
Expecting there to be a full review of a Chinese 7" Tablet with Phone functionality on Linuxslate.com at some point in the future would not be an unreasonable expectation.  Keep checking back.