Area code 818 did not exist until Jan 7, 1984, so we know that the 818 numbers at least were not written until then at the earliest. "(303) 293-2333" has belonged to a few different entities over time:
Currently: an attorney's office
Previous to that documented as far back as 10/16/87 : Mallon Company (still looking for earlier documented dates, if any)
http://docs.azgs.az.gov/OnlineAccessMineFiles/M-R/PilgrimMohave345a.pdf
April 1, 1984 edition of How to Find Missing Persons - CNA number for phone company
If she was using it as a CNA number, and it worked at the time she was using it, then she was probably making at least some of these notes between Jan 1984 and Oct 1987, assuming Oct 87 is when the number was first assigned to Mallon.
Ben Perkins used the address in the note page as early as 1983. It is also listed on Ancestry as his address in 1984. By 1990, he was disbarred. Other addresses for him are:
564 Fairview Av, Los Angeles, CA, 90033 (1990)
[614 E Manchester Blvd Ste 202b, Inglewood, CA, 90301-1996 (1996)]
[1860 W 38th Pl, Los Angeles, CA, 90062-1009 (1994)]
[1242 W 89th St, Los Angeles, CA, 90044-2026 (1993)]
[734 N Inglewood Ave Apt 3, Inglewood, CA, 90302-3783]
[5357 7th Ave Apt 2, Los Angeles, CA, 90043-2578]
It seems that the address she wrote for Ben was current for 1983-1990.
Based on the above, I think she wrote at least part of the notes, if not all, between Jan 1984, and Oct 1987.
Edited: Found a document with the 303-293-2333 number dated Jan 12,1987 for Mallon.
http://ocdimage.emnrd.state.nm.us/I...rt 8/ADA-03-00560 00001-10000/09073_04940.pdf