Hi everyone,
I figured this out and figured that I should post for posterity. There were three steps I had to take:
1. As expected, set the check box in 'ADE XL -> Editor Window -> Outputs -> Save All ... -> AHDL vars' to 'selected'
2. Write a Spectre file that specified which values to save, example below:
Code:save I32<200>:variable_name
save I18<1>:variable_name
...
3. Include the Spectre file useing 'ADE XL -> Editor Window -> Setup -> Model Libraries'
My guess for the syntax to use in step two was based on this document:
http://www.eecs.tufts.edu/~ryun01/gmid_ruida.pdf , and it worked. So thanks to the authors!