Hello everyone! I'm a newbie to websleuths though I have lurked for years. I did some digging around this evening based on the email in this thread from BK. Here's what I found:
1969 - 1984 Sambo’s open and active in Denver
http://www.santabarbara.com/Dining/review_read.asp?pk_restaurant=773
Which means, if he is referring to the "old Sambo's", it would have to be after 1984. However, for him to remember that it was originally a Sambo's, he would have had to have seen it close (perhaps ate there before it closed). Therefore, 1984 or earlier.
Next, the infamous Red Barn/antique store:
Old Red Barn now a Starbucks
Location according to Red Barn memory website is 2975 E Colfax Ave Denver, CO
http://www.barnbuster.net/barnsgonebye12.html
Street view on google maps estimates the address at around 2914 E Colfax Ave Denver, CO (if you'd like to take a look - can not tell what is across the street that he claimed had been many unsuccessful restaurants)
Opened(?) Or was active on April 23, 1969. (Source barnbuster.net)
Closed at the latest in 1986, as that is the year the final leases on Red Barn Stores were terminated.
http://en.wikipedia.org/wiki/Red_Barn
This is directly from the notes that I took while I was researching, so I mostly just stated the fact and source, just like high school report data.
Based on what I found above, I theorize that BK was active in Denver in the mid 80's to early 90's.