The bill proposing the "San Diego" Exposition half dollar was introduced in the House of Representatives by George Burnham (R-CA) in February 1935. A California colleague of Burnham, Representative Bertrand Wesley Gearhart (R-CA) introduced House Joint Resolution 224 in March 1935 in support of his "See America Year" initiative.
The Joint Resolution sought to authorize the President of the United States to proclaim each of the years of 1935 and 1936 as "See America Year." The Joint Resolution was referred to the Committee on the Judiciary. In support of his Resolution, Mr. Gearhart placed "Extended Remarks" in the
Congressional Record on May 2, 1935 - the "Remarks" were a transcript of a radio address Gearhart had made on April 23, 1935.
The primary message of Gearhart's address involved encouraging Americans to travel within their own country and see/experience the sights that the United States had to offer vs. foreign destinations. Not surprisingly, his focus was on California attractions such as Yosemite Valley, Sequoia National Park, San Francisco and the Golden Gate. He did, however, also reference the beauty of such locations as Glacier National Park in Montana, Yellowstone National Park (mostly in Wyoming) and the Grand Canyon in Arizona. (The American West was definitely his focus!)
He also made specific reference to San Diego and its Exposition - an event that was to take place in 1935 (and would be extended into 1936). He commented:
You, our easterners, have, perhaps, not visited the beautiful city of San Diego, where, during the balance of this year, there will be held an exposition - an exposition symbolizing the birth of a new era of development in the West. Here you may view the wonders of present-day industry and commerce - rare relics of art, the magical wonders of science - all amid surroundings exquisite in their architectural perfection.He didn't mention the commemorative half dollar, but it was not yet a done deal in Congress at the time of the address, so that was not too much of a surprise; the coin bill would be signed into law, however, just a few weeks later on May 14, 1935.
The City of San Diego and the Exposition Company likely hoped that Americans would act on Gearhart's suggestions and include San Diego and the Exposition on their travel itineraries. The City, and its local Tourist/Visitor organizations, were active in the promotion of the City and Expo!
Several years back, I came across a circa 1935 tourist/visitor information booklet that highlighted the Exposition and encouraged folks from across the country to come to the San Diego area for the Exposition and the many other sights and attractions the area had to offer. The booklet was prepared by the San Diego California Club, a group organized in 1919 "to act as an information and immigration bureau for the citizens of San Diego County and to the thousands of prospective settlers and visitors inquiring about the area." You'll notice on the front cover of the booklet (image below) is printed "COMPLIMENTS OF San Diego Chamber of Commerce." As the booklet was promoting area tourism in addition to the Exposition, and represented a tool by which the Chamber could support its mission of helping promote its member businesses, it's not a surprise to see its involvement.
So, while the booklet is not a piece of ephemera directly tied to the California-Pacific International Exposition Half Dollar or the Exposition Company, its promotion of the Exposition makes it a nice supplement to the coin - at least IMO!
San Diego and the Exposition Tourism Booklet - Front Cover
San Diego and the Exposition Tourism Booklet - Exposition Page #1
San Diego and the Exposition Tourism Booklet - Exposition Page #2
San Diego and the Exposition Tourism Booklet - Exposition Page #3
San Diego and the Exposition Tourism Booklet - Back Cover
1935-36 California-Pacific International Exposition Half Dollar

For more of my posts about commemorative coins and medals, including others about the "San Diego" Half Dollar, see:
Commems Collection.