I have a list of items separated by semicolons, because the items themselves contain commas. If this were a comma-separated list, I would offset it from the rest of the sentence with a comma, but I'm not sure what to do in the case of a semicolon-separated list:
While visiting Houston, TX; San Francisco, CA; and Atlanta, GA, I spoke to many different types of people.
Should there be a comma or a semicolon between "Atlanta, GA" and "I spoke"?
(I am hoping for answers that provide a grammar or style rule for what to do in this situation rather than a suggestion to restructure the sentence, unless the applicable grammar or style rule is "restructure sentences to avoid this situation".)