Dual Dc regulated voltage circuit design
First, you need to go back to the datasheet for the regulator.  There is a specification for minimum output load current.  My recollection is that value is 5 mA.

That current determines the value of the resistor connected from the output of the regulator to the Adj pin.  R3 &amp; R9 in your schematic diagrams.  

1.2V / 5 mA = 240 Ohms.  Note that 240 Ohms is used in all of the app notes for the regulators.

Note that you can now treat the regulator Adj pin (with that resistor installed) as a current source.  The output voltage is the voltage across the resistor from the Adj pin to ground PLUS 1.2V.  Because there is a constant 5 mA current from R3, it's easy to calculate the value of the resistor to ground.

Note that the value of R3 &amp; R9 can be changed to make things easier for you.  240 Ohms is the highest value you should use but you can safely go lower.  This may make it easier for you to pick a pot value that is more readily available.

Also note that your negative regulator can't be the same as the positive regulator unless you use separate unregulated supplies.  The negative regulator would need to be a LM137 (or LM337), not a 117 or 337.